To project overview

The Zea Harbour Project

Other Research Project | 02/05/2016

The Zea Harbour Project: Land and Underwater Archaeological Excavations of Ancient Athens’ Naval Bases in the Piraeus

The Zea Harbour Project – a combined land and underwater archaeological investigation of the ancient Athenian harbours of Zea and Mounichia – was launched in 2002 under the direction of Dr. Bjørn Lovén, Associate Professor in Maritime and Classical Archaeology at the University of Copenhagen. In historical terms, Athens in the Golden Age (the fifth and fourth centuries BC) achieved greatness because of the city’s immense fleet of three-banked warships called triremes. The fleet projected Athenian power overseas, employed citizens to operate its rowing benches, fought off the Persian threat, protected commercial shipping from predator states and pirates, and enforced the collection of tribute from allies. The triremes themselves have yet to be found, but the naval installations have left a large archaeological footprint both on land and especially under the sea. The project’s mission is to survey, excavate, and publish the archaeological remains of these naval bases in the Piraeus, including the harbour fortifications and the shipsheds that housed the fleet. Further, the Zea Harbour Project focuses on presenting these important monuments, the very backbone of the world’s first democracy, to the public. This article discusses the discoveries made between 2002 and 2012 by the Zea Harbour Project.


Satellite photo the modern Piraeus showing the configurations of the three harbours, Kantharos, Zea, and Mounichia. Photo: GoogleEarthPro

Between 2002 and 2012, a team of archaeologists and other specialists led by underwater archaeologist Dr. Bjørn Lovén excavated and investigated extensive portions of Athens’ harbour city, the Piraeus. The naval bases in the Piraeus rank among the largest building complexes of the ancient world and housed the enormous fleet of the young Athenian democracy.

The Athenian Democracy – Baptism by Fire

The fifth and fourth centuries BC saw the Golden Age of the city-state of Athens. These centuries witnessed explosive development not only in democracy, but also in lawgiving, art, architecture, science, and philosophy, all of which continues to reverberate in our time. It was during this period that the foundations of Western Civilisation were established.

The Piraeus is a city on the coast south of Athens. It was the harbour city of Athens in antiquity and remains so today.

The historical framework for the impressive finds of the Zea Harbour Project began on one of the last days of September 480 BC. Around 80,000 men of the Greek fleet (half of them from Athens) gathered on the beaches of Salamis, the island that lies opposite the Piraeus. As they boarded their warships, they saw their homes and sanctuaries burning on the other side of the strait, the flames bright in the night sky. The Persian army, which had travelled thousands of miles to conquer Greece, had laid waste the entire territory and city, including the Acropolis. 

At dawn, Xerxes, king of Persia, sat down on his portable throne and turned his gaze towards the sea, where his enormous fleet, numbering around a thousand warships manned by some 200,000 men, approached the Strait of Salamis, oar stroke by oar stroke. The allied Greeks had just 400 warships. Xerxes was confident in victory, but he underestimated the willpower of men fighting with their backs to the wall.

Few moments in world history have been so significant, as the victory of the Greek fleet that day saved the young Athenian democracy and the rest of Greece from the yoke of the Persian king. It is difficult to predict what would have happened if the Greek fleet had lost at Salamis, but it is clear that a Persian victory would have had immense consequences for subsequent cultural and social developments in Europe. The victory at Salamis rightly echoes through history and awakens awe and inspiration around the world today.

An archaeologist excavates the early shipsheds at Mounichia Harbour in the Piraeus. Vassilis Tsiairis took this photograph on one of the very rare days of good visibility.

The Greatest Catch

It was an old fisherman named Mitsakos who in 2010 guided the Zea Harbour Project to the naval bases from the time around the Battle of Salamis. As a child, he fished while sitting on an ancient column rising from the sea on the northern side of Mikrolimano Harbour in the Piraeus, on what was once part of the ancient naval base called Mounichia. The project had previously investigated this area and found only a few dislocated ancient blocks. 

The Zea Harbour Project is a collaboration between the Greek Ministry of Culture and the Danish Institute at Athens. The Carlsberg Foundation has contributed 14 million Danish Kroner in funding to the project.

This part of the harbour is a maze of anchors, mooring chains, and modern debris. On most days, one can only see 20–50 centimetres underwater. Mitsakos guided two divers to the location, and they surfaced with wide smiles and shining eyes. In a relatively short time, they had found an ancient monumental wall and several large foundation blocks in three colonnades.

Between 2010 and 2012, six shipsheds were excavated here using digital, three-dimensional survey methods that improved over the course of the project and showed their scientific strengths. Day by day, the researchers updated their plan in detail, and although the divers could not see both ends of the same block, they always knew exactly where they were. The digital survey team immediately produced outstanding results. Based on pottery and a C-14 date of a worked piece of wood found in the foundations of a colonnade, the researchers could date the first building phase to 520-480 BC, or shortly afterwards.

“It is fascinating to imagine that some of the Athenian warships that fought at Salamis in 480 BC were most probably housed in these shipsheds. No doubt they represent our most important results,” says project director Bjørn Lovén.

The Golden Age of Athens and the Piraeus

Two years after the Battle of Salamis (478 BC), the Athenians and their allies founded the Delian League with the avowed aim to punish the Persians for their aggressions and to guard against new attacks. Athens exploited this alliance to strengthen her position of power in the Mediterranean and Black Seas. Over the next five decades, Athens developed into a superpower – economically, militarily, and culturally. The size of the fleet doubled from just under 200 to around 400 warships of the trireme class. The Zea Harbour Project discovered and documented 15 shipsheds from this important historical era, distributed along 132 meters of coastline on the eastern side of Zea Harbour.

The area was a complicated puzzle of architectural elements, such as column bases, walls, ramps, and side-passages, all belonging to seven different types of slipways and shipsheds built over more than 150 years. Normally, it is relatively easy to separate and date building phases based on excavated, undisturbed layers. This is because some of the finds found in these layers can be dated. However, in this area the researchers found mostly rock-cut foundations in the bedrock and worked blocks: it was a jumble of several slipways and shipsheds built on top of each other.        

It took several years of research to sort out the different pieces of the puzzle, then to discern the individual buildings to which they belong and understand when they were constructed in relation to one another. The researchers also succeeded in merging their three-dimensional digital plan of the shipsheds with the 1885 plan of the same area produced by the famous German architect and archaeologist Wilhelm Dörpfeld. This allowed them to integrate important parts of the shipsheds that are hidden today under the modern waterfront into their overall plan, with great precision. One very important result was the definition of the upper end of the fifth-century BC shipsheds, today hidden under the ring road surrounding Zea Harbour. 

Mounichia Harbour, Piraeus. Archaeologists document the 10 x 10 meter square tower M-T3 on the southern fortified mole using digital survey techniques. Photo: Bjørn Lovén

Greatness and Decline

In 431 BC, the Peloponnesian War broke out between Athens and Sparta, Greece’s other superpower. In the first years of the war, the three harbour entrances of Kantharos, Zea, and Mounichia were fortified after a failed Spartan sneak attack on the Piraeus. 

One of the main objectives of the Zea Harbour Project was to excavate and document the harbour fortifications of Zea and Mounichia. Their monumental size astonished the researchers. At Mounichia, they followed the 10-metre-wide southern fortified mole for a length of 146 metres. This massive structure was in the region of 10 to 15 metres tall in antiquity. On the northern fortified mole, the 13-metre-wide entrance tower is preserved to a height of 9 metres above the seabed.

As Bjørn Lovén explains, “It was an impressive sight that met travellers sailing past Piraeus’ fortified naval bases in antiquity – no one would doubt the naval power of Athens.”

’Happy Hour’ in Athens’ Second Golden Age

The so-called ‘double-unit shipsheds’ –– another important discovery of the Zea Harbour Project –– were constructed during the Second Golden Age of Athens in the fourth century BC. By this time the Athenians had quite simply ran out of shoreline within the basins of the naval harbours. As a result, they decided to construct shipsheds twice as long in order to make room for two warships stored end-to-end. In this way, they could accommodate twice as many warships on the same length of shoreline. With the discovery and investigations of the double-shipsheds, the Zea Harbour Project has demonstrated that the naval bases in the Piraeus are among the largest building complexes of Antiquity. 

The harbours of the Piraeus are heavily polluted. Archaeologists wore chemical-resistant Viking Pro 1000 drysuits and Interspiro full-face masks with positive-pressure valves. Such equipment completely seals the diver from the contaminated underwater environment of the harbour basins.

In the so-called Group 1 shipshed complex, around 640 columns and four sidewalls supported roofs that covered an estimated area of about 13,000 square metres – an area corresponding to just under two football fields. These 22 double-ship sheds were around 80–90 metres in length, 6.5 metres wide and 7.5 metres tall. This single structure housed 44 triremes, which would have been crewed by about 8,800 men. It should be noted that the Group 1 shipsheds only account for just under 12% of the total number of shipsheds. When the naval bases were fully developed, they covered around 110,000 m2.

When Zea Harbour was deepened by dredging in the 1960s, the lower ends of the best-preserved double-shipsheds were destroyed. Today, the upper 60 metres of these buildings are preserved, 20 metres of which are located in the sea. The theoretical reconstruction of the total length of the double-shipsheds hinges on the identification of the coastline in antiquity, since the shipsheds obviously had to reach the sea. The shipsheds and the coastal fortifications of Mounichia Harbour were instrumental in determining that there has been at least a 2.25 metre rise in relative sea level between the fifth century BC and today. The rise in sea level has submerged 40 to 50 metres of the ancient harbour front. This discovery – considered one of the project’s most important results – has had a dramatic effect on our understanding of the topography of the Piraeus.

3D reconstruction of the double-unit shipsheds at Zea Harbour. 3D reconstruction: Brian Klejn-Christensen

Just Before Closing Time

In 325 BC, in the twilight hour of Athens’ Second Golden Age, the city introduced a new type of warship, the so-called penteres (‘five’). These powerful warships, crewed by 380 men each, had an estimated length of 45 metres. On the south-eastern side of Zea Harbour were excavated seven unroofed slipways, each measuring eight metres wide and preserved for a length of 43 metres. In all probability, these were built to accommodate this new type of warship. Previously, naval structures for larger warships have only been found on the island of Rhodes and at Carthage.   

Director Bjørn Lovén explains that he could not get the pieces of the puzzle to fall into place in this area of Zea Harbour. 

“We had the feeling that these structures and rock cuttings were very important, and it was in the last moment under the final excavation campaign in 2012 that the three-dimensional patterns of the rock-cut foundations in the bedrock finally made sense. Based on this regular matrix in the foundations of the buildings, we could quickly excavate the wide slipways.”

Artistic reconstruction of a penteres (‘five’) and the wide slipways at Zea Harbour. Illustration: Yiannis Nakas

It is ironic that the fully developed naval bases of the Piraeus were under Athenian control for only a few years. In 322 BC, Athens lost control of the sea when a Macedonian fleet defeated 200 Athenian warships off the Cycladic island of Amorgos. New naval technology did not save the city. In fact, domination of the Mediterranean Sea (including the Piraeus) passed to the Macedonian kings, thus ending the Golden Age of Athens.

Scientific Social Responsibility Aspects

Bjørn Lovén describes the Scientific Social Responsibility (SSR) aspects of the Zea Harbour Project in the following way: 

“Recently I watched the first episode of the BBC documentary ‘Building the Ancient City: Athens and Rome’, in which the Zea Harbour Project is featured. To my knowledge, it is the first documentary on Ancient Athens that places the commercial and naval harbours of the Piraeus at the same historical and archaeological level of importance as the Acropolis, the Agora, the Pnyx and the Kerameikos. This is where the Emporion (commercial harbour), the shipsheds, Philon’s Arsenal, and the monumental costal and harbour fortifications of the Piraeus rightfully belong. For me, showing this accurate history of Athens and the Piraeus to the general public is the greatest achievement of the Zea Harbour Project and all the people and institutions that have supported us over the years!”

Further, Bjørn Lovén states: 

“Compared to other archaeological projects, we rely on a large professional staff, and take relatively few students. We have a strong focus on student talent development and specialisations, and the students that have been trained on the Zea Harbour Project are performing extremely well in their subsequent careers”

Based on student participation in the Zea Harbour Project summer school the former Dean of Career Development at Yale wrote: 

“He [Bjørn Lovén] is determined that each student derives the maximum benefit from the situation and that each student's particular interests be recognised and incorporated into the study. This has led to extremely positive experiences and wonderful student reviews in our post-programme assessment phase. Without question, from a field of over 200 opportunities worldwide, Zea is one of our most successful.” 

Bjørn Lovén emphasises: 

“Credit for this success, and our overall success, must go to each member of the team.”

A Special Thanks

Bjørn Lovén describes the importance of the Carlsberg Foundation for his research: 

“Jacobsen’s vison has been critical in maintaining the strong position of Danish Classical Archaeology internationally, and I can thank the Carlsberg Foundation for my career. Our excavations in the Piraeus are among the most complicated in the history of archaeology, and very resource demanding in terms of both time and funds. One cannot ask the Danish State for 14 million Danish Kroner in risk-bearing funding, and the Zea Harbour Project could not have been accomplished without the support from the Carlsberg Foundation. Excavations are obviously the very foundations of archaeological research, since excavations produce almost all primary research results.”

Selected Scientific Bibliography: 

Lovén, B., The Ancient Harbours of the Piraeus, Volume I.1, The Zea Shipsheds and Slipways: Architecture and Topography, Monographs of the Danish Institute at Athens 15,1 (Aarhus 2011). [Peer-reviewed]

Lovén, B. & Schaldemose, M., The Ancient Harbours of the Piraeus, Volume I.2, The Zea Shipsheds and Slipways: Finds, Area 1 Shipshed Roof Reconstructions and Feature Catalogue, Monographs of the Danish Institute at Athens 15,2 (Aarhus 2011). [Peer-reviewed]

Review of Volume I.1 & I.2: (1) Bryn Mawr Classical Reviews. Link: http://bmcr.brynmawr.edu/2013/2013-02-39.html; (2) Gnomon 86/1, pages 49–58 (2014). 

Lovén, B. & Sapountzis, I., The Ancient Harbours of the Piraeus, Volume II, Zea Harbour: the Group 1 and 2 Shipsheds and Slipways – Architecture, Topography and Finds. Monographs of the Danish Institute at Athens 15,3 (Aarhus, forthcoming spring 2016). [Peer-reviewed]

Most Important Media Exposure:

BBC, the Zea Harbour Project is featured in the documentary ‘Building the Ancient City: Athens and Rome’ (aired August 2015). 

National Geographic Television, the Zea Harbour project will be featured in the documentary ‘The Greeks’ (airs 2016). 

TV2 FRI, the Zea Harbour Project is featured in the Danish documentary 'Nordkaperen i Grækenland' by the famous Danish adventurer Troels Kløvedal (aired March 2016)

Further, the Zea Harbour project has been featured in radio interviews and numerous newspaper and magazine articles.