The Greek archipelago cosists of around 3000 islands with the largest ones present in the default FS scenery. Many islands are popular holiday destinations with larger airports. The airports are often located parallel to the coast due to mountaineous terrain which sometimes results in spetacular approaches. Also see the Athens page. Find comprehensive freeware scenery add-ons on this site.
There is plenty of places in the achipelago to visit. Here is a couple of IFR flights:
Athens (LGAV) - Crete (LGIR) (~0.5 hour). Crete is the largest island of Greece and a popular holiday destination. The airport has a nice approach. There is only straight-in approach for runway 27 probably due to terrain.
Athens (LGAV) - Cyprus (LCLK) (~1 hour). Even though Cyprus is not part of Greece, this tours crosses the archipelago.