Kalymnos has been one of Europe's leading sport-climbing destinations since 1997, when Italian climber Andrea di Bari bolted the island's first 43 routes across the Arhi, Odyssey and Poets sectors. Magazine coverage and a run of climbing festivals through the 2000s spread its reputation, and by 2009 Adam Ondra had climbed Greece's first 9a route here, Los Revolucionarios. The 2023 guidebook counted more than 4,300 routes across dozens of sectors, from the stalactite-hung Grande Grotta to gentler walls above Masouri, with new lines still being bolted most years. Spring and autumn are the best months, when climbers work shaded cliffs in the morning and swim in the afternoon.

Old kalderimia, the stone paths that once linked the villages and monasteries, also make for good walking, from an easy route into Kantouni Bay to the climb up Prophitis Ilias, the island's highest peak at 676 metres; a marked long-distance route, the Kalymnos Trail, crosses the island for experienced trekkers. Along the coast, a dive centre works out of the cove at Gefyra, and deeper water off Therma draws more advanced divers.

Kalymnos was a sponge-diving island long before it was a climbing one, a trade the island traces back to antiquity and that Homer, Aristotle and Plato all mention. Divers originally worked with only a weighted stone, the skandalopetra, to reach the seabed; after 1865 the skafandro diving suit let crews go far deeper and stay down far longer, and Kalymnos built a fleet of some 300 boats that worked sponge grounds across the Mediterranean. The cost was severe: between 1886 and 1910, decompression sickness is estimated to have killed around 10,000 divers and permanently disabled another 20,000, a trauma still commemorated in the island's own Sponge Diver's Dance, choreographed in the 1950s and performed at local festivals to this day.

The industry collapsed almost overnight in the 1980s, when disease wiped out much of the sponge population across the eastern Mediterranean, and the fleet shrank from around 30 boats to four. Sponges are still sold from workshops in Pothia, and the town's Maritime Museum keeps the fuller history, alongside neoclassical buildings left from the Italian administration of 1912-1947.

Pothia, the capital and main port, is where most of that seafaring history is visible, in neoclassical facades and in the Church of the Transfiguration, whose marble iconostasis was carved by sculptor Giannoulis Halepas. Chorio, three kilometres inland, was the island's fortified capital before Pothia grew up around the port, and its hilltop Castle of Chora and Pera Kastro were built to keep villagers safe from pirate raids.

The west coast around Myrties and Masouri has become the island's tourism and climbing base, facing the small islet of Telendos across an 800-metre strait; boats cross regularly, since Telendos itself has no cars and only around 60 residents, having been cut off from Kalymnos by an earthquake in the 6th century AD. Vathys, in the north-east, sits in the island's most fertile valley, its fjord-like inlet at Rina used mostly by small boats.

Kalymnos isn't primarily a beach island, but a handful are worth planning around. Vlychadia, about 6 kilometres from Pothia, has fine sand and clear water good for snorkeling, while Akti, a little further out, is known for its turquoise-to-emerald colour and gently sloping seabed. Closer to town, the small cove at Gefyra is pebbly rather than sandy, but an easy walk from the centre, with a taverna and a dive centre right on the water.

On the west coast, Melitsahas and Kantouni both have genuine sand, backed by low cliffs or shady trees, and stay relatively quiet even in summer, while Masouri, the busiest of the group, is fully organised with sunbeds and water sports and gets crowded in July and August. None of these are large beaches by island standards, so arriving early in high season still pays off.