The accessible centre of Nisyros's active caldera
Stefanos is the largest and most accessible hydrothermal crater in the Lakki caldera. The descent reveals a pale basin marked by mineral deposits, fissures and steam vents, with the surrounding rim making clear that this is part of a much larger volcanic system. Arriving early creates a calmer visit and avoids the strongest heat and the main wave of Kos excursion traffic.
Treat every barrier as a safety instruction. Wear closed shoes with grip, remain on the authorised route and never touch vents, test the ground or collect minerals. Sulphurous gas and heat can affect visitors with respiratory or cardiovascular conditions; seek current local advice and turn back if unwell. Access may close because of volcanic monitoring, weather or maintenance. There is little shade, so carry water and do not bring pets onto the crater floor.
Good to know
Volcano, Caldera, Geology, Safety, and Early visit
