Rhodes (Ρόδος)
Worth a day or two's visit on the way to less touristy islands, if only to explore the fascinating old town.
Don't know much about the rest of the island except to avoid the party town of Faliraki. It is the largest of the Dodecanese islands and there are direct flights from the UK. The ancient town of Lindos and its acropolis, on the southern part of the island, are well worth a visit.