Caldera – Crater
The volcano of Nisyros is the newest active volcano in Greece since its oldest rocks do not exceed 150,000 years of age. 60,000 years ago to this day, hundreds of small eruptions built a cone that rose about 600 metres above sea level and had roughly the perimeter of the island as it is today.
Two huge explosions, 25,000 and 15,000 years ago, destroy the central part of the volcano, which caves in and creates the current caldera of the volcano. Since then the volcano remains at rest. But the hot rocks, located a few kilometres in depth underneath the caldera and their hot gases, warm the seawater and the rainwater that circulates around the more shallow rocks and convert it into superheated liquid at temperatures approaching the 500 degrees Celsius. Intermittently, the superheated liquid ejects into the air the rocks that prevent it from reaching the surface, causing hydrothermal explosions and creating hydrothermal craters. Such explosions were recorded in Nisyros in historical times.
Stefanos is the largest and most impressive of the 10 craters and monopolizes the interest of visitors, as it seems to them that this is the “volcano”. It is one of the largest and best-preserved hydrothermal craters in the world, it has ellipsoid shape with its longer axis at 330 meters and the smaller at 260 meters, while its depth reaches 27 meters. We don’t know its exact age, like with most craters, but it is calculated that it can’t be more than 3,000 to 4,000 years old. Every visitor can follow a trail to reach the inside of the crater and admire the space and its unique steam activity up-close.
Palaiokastro
Palaiokastro is the fortress of the ancient city of Nisyros and one of the best preserved in the Aegean area. The ancient city was built at least since the 8th century BC, above the modern settlement of Mandraki. The wall, as it survives today, dates back to the 4th century BC. Built on the brow and the slopes of the hill it led to the cliff from its west side, whilst from its north, it reached up to the rock where the medieval castle and the monastery of Panagia Spiliani lie today.
The total length of the fort is very large. The wall and the cliff mark an area of approximately 130.000 m2, with total perimeter of almost 2 km, while the weight of some of the stones that make up the wall reaches 3.5 tons. The construction of the costly and strong fortifications could be attributed to the effort of the tyrant of Caria Mausolus and his successors, who for a short time (355-332 BC) had acquired control of Rhodes, Kos, and the neighbouring islands, to create a powerful defensive front in the region. The local volcanic black stone (basaltic andesite) was used for its construction. Palaiokastro is located in the village of Mandraki and the admission is free.
Panagia Spiliani
