The Greek city of Apollonia has an underwater area of ruins 800m x 300m, that is 24hectares or 60 acres.
The walls of buildings on the sea floor include warehouses, quays, slipways for warships, roads, houses, and a submerged corridor or tunnel with the roof intact underwater.
The survey method worked at three scales: positioning the corners of buildings on the whole map of the city; measuring the exact dimensions and details of buildings with a 50m wire tape; and measuring sizes of building blocks, thickness of walls, width of windows, and other small features with measuring rules or rods.
The overall accuracy of buildings on the map is correct to an error of +/- 20cm, and for small items such as block sizes the error is +/- 2cm. These maps show the results of the work by divers. The original large scale maps were drawn on site at Apollonia in 1958 by Nick Wood, shown in this picture.
Map of the whole city of Apollonia, near Benghazi. It was founded by Greeks in about 635BC. The shaded area is the modern beach, so everything north of that is underwater, except the islands at the seaward edge of the city. The map was made by measuring the position of poles held by divers hovering over the corners of each building in turn. The baseline for the survey was from the gate tower in the west, to the theatre in the east.
Architect’s drawing by Nick Wood showing the submerged southern tower or Block Fort that
guarded the entrance channel into the harbour. Block sizes were measured by divers working with rulers, and making drawings on plastic boards.
Architect’s drawing by Nick Wood. The submerged Apse building on top of the Grid Building. Apollonia was occupied for over 1000 years, and there were many successive levels of building, some because of earthquakes. The darker shades of stonework in the Apse building show the number of courses. There are at least 4 successive stages or periods of building. Distances of more than a few metres were measured by a wire tape mounted on a chest reel carried by a diver.
The Great Piscina is now completely underwater, and is illustrated in this drawing by Nic Flemming. The numbers on each surface show the depth in metres below present sea level. Pools like this in Roman times, 2000 years ago, were used to preserve and cultivate sea fish, and as relaxing decorative places, with statues and ornamented. The water was kept fresh and oxygenated by circulation through several channels that could be opened or closed with perforated sluice gates. This is one o the earliest drawings of a Piscina, and many more were discovered around the Mediterranean and measured in the 1960s and 70s
The ten slipways are carved out of the solid bedrock om the West Island at Apollonia. They are Greek in origin, dating about 2500 years ago, and are 40m long, 6m wide, and slope at 4 degrees. They were used to store lightweight fighting galleys that would have been damaged by attached algae if left in the water. Some of the slipways have a raised central stone runner. Some of these have a central groove that probably contained a timber beam. The slipways are totally submerged now, but would originally have had only one quarter of their length in the sea. Walls of later buildings have been constructed on top of the slipways when they lapsed from use.