Didymo is the second tallest mountain of the region, the first being Arachnaio. Its has two main peaks, the highest of which reaches an altitude of 1.121m. There are other, lower peaks, namely “Profitis Ilias” (1.068), “Tourla” (858m), “Raches Gravas” (569m). To the east, it is merged with the heights of the Aderes mountain range. The semi-mountainous and plainy parts of the Ermionida region can be found over to its south foothills.
The name of the mountain seems to come from the “Dioskouroi”, the pair of twin demigods Castor and Pollux (or “Polydeuces”). The peaks of the mountain are devoted to them (“Didymo” means “twin” in Greek, hence the name).
The mountain's geological identity is of notable interest, as it contains two impressive caves at the foothills of its endpoints. The so-called “dolines” of Didymo are craters made from a subsidence of the ground, as well as rockfalls of the carbon-based rocks of the area. It is also noteworthy that inside one of these caves, there is a small church. Close to that area, located in a basin, visitors can find a settlement of the same name (Didymo). There are three small live-stock farm settlements located on its slopes: 'Rados' and 'Pelei' in the north, and 'Loukaiti' to the southeast. The Byzantine Monastery of Avgo, to the north, over the canyon of the river Rados (called “Sella” in ancient times”) is worth a visit. It dates back to the 14th century A.D. and has been renovated.
On the Didymo mountain, the amount of flora is low, while a certain species of juniper is the most common type of plant there. Taller trees, like plane trees (or 'Platanus') can be found on the mountain's north side. Furthermore, antennae and wind-farms have been built on its peak and heights. There is also a freeway passing through the mountain, the construction of which has 'bisected' it. Lastly, there have been some ecological concerns lately about the operation of waste-baling machines in the area, raising the issue of fortifying the public health and safety services.