The islet of Patroklos, or Gaidouronissi (“the island of the donkeys”) as it is also called, is a small islet situated at the southern part of Saronicos Bay, just across the beach of Harakas; the islet belongs to the territory of Keratea. It owes its official name to the general of Ptolemy, named Patroclos, whose fleet berthed here, during his expedition in Attica in the Hellenistic period.

As the islet has several well protected coves, several fish farming installations have been established here. An excellent sandy beach, ideal for swimming and well protected from winds of any direction is found within a small cove at the northern coast, close to one of the fish farming installations. In the past the islet had also a tavern, the owner of which used to bring people on the island by a private motor boat he had for this purpose. The islet is very close both to the opposite coast, from which it is found only some 1000 meters away and from the boat slide of Anavyssos, from which the distance is about 1,5 nautical mile.