Our study focuses on remains of shipsheds, in particular a ramp used to pull warships out of the water and keep them protected under cover during winter. This ramp was constructed between approximately 250-225 BC and some decades later it was repaved, after a major earthquake destroyed the town of Rhodes and most probably the harbour and sheltered ships, as historical evidence reveals. 300 years later the harbour was to a great part abandoned because of a coastal uplift. The only reasonable explanation for the ramp reconstruction was to counteract a 1 m seismic subsidence at around 220 BC or earlier. Several possible explanations can be proposed for the earthquake which produced seismic subsidence alternating with uplift in Rhodes, in a pattern of vertical motions different from that observed in Crete, or other convergent boundaries.