The Cave of Antiparos is one of the most impressive stalactite caves in the Mediterranean and one of the longest-known tourist attractions in Europe — visitors have been making the journey here since the 15th century, scratching their names into the formations as they went. The cave descends about 70 metres into the mountain above the village of Agios Ioannis, reached by a path and then a long flight of concrete steps into the hillside.
The interior is spectacular: tall chambers with stalactites and stalagmites that have been growing for millions of years, the largest formations reaching several metres in height. The cave maintains a constant cool temperature year-round, which makes it a relief in summer. A guide leads groups through the lit section; the deeper, unlit portions are not accessible to the public. The cave is open from late morning to early afternoon during the summer season; check locally for current hours.