With only 300 people still living on the island, the rest have emigrated to Perth, Australia with thousands returning every summer and far out-weighing the residents.
The Knights of St. John Hospitallers left a castle on the island which is the main historical attraction but the Dorian Citadel of Paleokastro is a close second.
There is a famous cave/grotto with an enormous chamber of stalactites and several churches and monasteries all worth exploring. Kastellorizo has no beaches but plenty of rocks to swim from instead.
At first glance, the main port is lovely but off the main drag has been destroyed by an ammunition explosion during WW II leaving an eerie deserted feeling to it. Still the prices are right and there are several good tavernas to choose from and many rooms.