The ruins of Cnidus, an important ancient city in southwestern Asia Minor, lie directly on an earthquake fault - the Cnidus Fault. Offset and deformed archaeological remains along the trace of the fault testify to its recent activation. The ancient city's famous Round Temple of Aphrodite is vertically offset by 0.35 m across the fault. The fault also forms the back wall to the Sanctuary of Demeter where Roman-age walls are displaced and deformed by slip on the fault. Archaeological evidence suggests multiple episodes of abrupt destruction at the site and, in the Sanctuary of Demeter, indicates past earthquake surface rupture on the Cnidus Fault. Other evidence of seismic damage is apparent at the site, most notably the parallel collapse of columns in a former stoa/row of shops, which directly overlie a destruction level dated by archaeologists to the 5th century AD. Together, the geological and archaeological evidence points to at least two major seismic events affecting the site. The first event, around the late Hellenistic period (2nd-3rd century BC), caused the destruction of the original Round Temple and of a temple in the Sanctuary of Demeter. The second event involved surface rupture of the Cnidus Fault and was responsible for the dislocation of the replacement Round Temple and the later walls of the Sanctuary of Demeter. In both cases, the archaeological evidence is consistent with a late Roman to early Byzantine age for this second event, which, if contemporaneous with the 5th century AD destruction of the stoa, supports an historical account of the city being devastated by an earthquake in AD 459.