The main port and town is Mandraki on the northwest side. Its white-washed houses contrast with the dark somberness of the volcanic rock. There are rooms to let and small hotels, and the bus hub. Many day trippers from Kos alight here.
Mandraki has a 14th Century kastro and monastery. The former castle is of the Knights of St John, high on the cliff face. Moni Panagias Spilianis (Our Lady of the Cave) is within the kastro. Inside the monastery is a Russian-style icon and icons that were used to hide the silver treasures of the church in plain sight.
You pass the Historical and Folk Museum on the way up to the kastro. The museum contains a reconstructed traditional kitchen.
Almost round, Nisyros' center contains the volcano's still active crater called Stephanos. Stephanos Crater (or Stefanos Crater) has hot springs, boiling mud pots, and gas vents. Buses leave for the volcano regularly, although you can walk down from Nikia and enjoy wonderful views on the way.
The main crater is 260 meters in diameter and smells of sulfur with hot vapors issuing from the soft ground. Steps lead down into the crater 30 meters deep. There is an occasional sulphur crystal.
Tours of the crater are very popular and care should be exercised not to step off the marked paths as the ground is brittle is some spots. The huge caldera contains several mini-craters.
There are beaches at Chochlaki and Miramare, which has better food than swimming. Gialiskari, or White Beach, is good swimming. Its near the thermal spa of Loutra, open June to October only.
The fishing village of Pali has shady, dark volcanic beaches and some rudimentary catacombs. The island's best beach is at Lyes. The white sand and great snorkelling make this a good choice.