At the moment there seem to be dangerous stray dogs in the gorge at Sousaki Volcano! Apparently they have already attacked visitors and seriously injured them.
If you are on the way from Athens towards Corinth, you will see a strikingly colored gorge at the oil refineries on the right side of the mountain slope. It hides part of a 20-30 million year old volcano that still shows signs of activity. Even if it hasn't broken out for a long time, there are still active fumaroles (hot gas escapes) and mofettes (dangerous carbon dioxide gases). In the past, sulfur and alum were mined here to a small extent. There are a few caves that are better not to be entered! They emit carbon dioxide gas that you cannot smell. Choking hazard! Even when there is no wind, you should not enter the gorge. On the front part there are most fumaroles and also a place where numerous gypsum crystals have formed.
The hydrothermal activity that deposited ores can be seen in many rust-red spots. These ores are usually already heavily weathered. There is pyrite, chalcopyrite and arsenopyrite (toxic!). Blue chalcantite can be discovered as secondary minerals. A few decades ago, the geological bureau also drilled to see if the area could be used geothermally.
There are other, much older volcanic rocks in the region and at Loutraki there are several dykes (formerly volcanic vents) that contain dacite. There is also hydrothermal deposits of jasper and probably also of opal and agate.