A short sail from Athens is Aegina island, a place with a rich history and very popular weekend destination for Athenians. The island has nice family beaches and seaside villages making it the perfect spot for a summer break.
There is also lots of archaeological sites to visit on the island, including the Ancient temple of Athena Aphaia and the ghost village of Paleochora. The island is also famous for its large production of pistachios.
The main town on the island is lovely and you can enjoy a nice stroll along the port promenade and the narrow streets. This is a great place to stop for an evening or even just to anchor off for a spot of lunch and swim by the beach.