Didyma (Δίδυμα) is a historic village in the prefecture of Argolida in Greece. Until World War II, the village was called Didymoi (Δίδυμοι), which means twins in Greek. The origin of the name is explained in two ways, first that it came from Mount Didymos or that it was adopted by the Twin Caves just outside the village. The two large caves are crater-shaped and impressive due to their size. They were probably formed by landslides and are about the same diameter, so the locals called them Twin Caves, Twin Craters or Dolines.
The largest cave is located at the foot of the mountain and is called Big Cave (Μεγάλη Σπηλιά) and the other, in the plain, is called Small Cave (Μικρή Σπηλιά). Prehistoric people took refuge there to protect themselves from natural phenomena, while during the Turkish occupation, the inhabitants of the area transported nitro from the animals' urine from the Big Cave and made gunpowder for their weapons.
When you arrive at the area, just outside the village (you should follow the relevant signs), you meet first the Small Cave and you reach it through a small cavernous entrance, carved into the rock. The crater has a depth of 80 meters in the alluvial layers and its diameter is 150 meters. Inside you encounter completely different vegetation in relation to the surrounding area and two small churches also carved into the rock, Agios Georgios (Άγιος Γεώργιος) and Metamorfosis (Μεταμόρφωση).
The Byzantine church of Agios Georgios, which is the first you meet, right next to the entrance, dates back to the 13th Century and has a historical inscription that marks the passage of Thomas the Palaiologos, Hegemon of the Peloponnese as well as an old stone font. The second church, Metamorfosis, is located on the Northside of the crater and its construction could not be dated. In addition to the two churches, in the cave, you could also see a deep hole in the ground, which is called Askitario (Ασκηταριό) which according to the local tradition it was created by the spear of Saint George (Agios Georgios) and was used from the 11th century as a place of solitude for monks.
Another tradition connects the Small Cave of Didyma with the Homeric Odyssey. It said that it was the cave where Odysseus and his companions hid after their escape from the cave of Cyclops Polyphemus, before they continuing their journey to Ithaca. Although this tradition seems a bit exaggerated, it adds another interesting aspect to the cave.
The Big Cave, a few hundred meters after the Small, offers an impressive spectacle with its size, but it does not house monuments. It is used as a refuge by many species of birds and during a walk in it, you could admire the huge granite walls around you.
Both caves are easy accessible by car (you could find them easily on Google Maps here) and there is no entrance fee.