The pleasures of Greece are simple but intense: diving from a yacht into water so clear that you glimpse pebbles on the sea floor 50 feet below; turning over a fragment of white marble to find marks left by a chisel 2,500 years ago; sitting in the shade of a quayside awning to eat lightly grilled fish served with lemon, oil and fresh oregano; and watching the sun descend into the Aegean with a glass of chilled white wine from Santorini and a dish of olives from Kalamata. Travelers often treat Athens as a necessary stop en route to the islands or a cruise, but the Greek capital has become a destination in its own right.