In the first half of the second century AD, the Roman fleet in British waters, the Classis Britannica, selected Dover as its headquarters on the British side of the Channel (it had another base on the French side, in Boulogne). As its base it built a large fort, covering more than two acres, on a shoulder of land below the Western Heights. A fort was laid out about AD 115-120 but was never completed. A second fort was built about AD 130-140 on a similar alignment, and this fort was completed.The army style fort was surrounded by a defensive wall and contained a headquarters building, at least two granaries and barracks. The buildings were separated from each other by wide metalled roads, along which ran drains and piped water.
Two massive stone lighthouses were built on the cliffs either side of the town to guide ships from France into the harbour. One of the lighthouses, known as the pharos, can still be seen in Dover Castle, and is the tallest surviving Roman building in Britain. To the north of the fort was an extensive civilian settlement containing many substantial buildings, including the Roman Painted House (built around AD 200) and a military bath house (built around AD 140-160). Early in the third century AD the Classis Britannica left Dover, never to return. The fort was abandoned and soil accumulated over the remains until the building of the Saxon Shore Fort.