Níssyros's central, dormant volcano gives the island its special character and fosters the growth of the abundant vegetation - and no stay would be complete without a visit. When excursion boats arrive from Kós, several agency coaches and usually one of the public buses are pressed into service to take customers into the interior. These tours tend to monopolize the crater floor between 11am and 2pm, so if you want solitude, use early-morning or late-afternoon scheduled buses to Nikiá (three daily continue to the crater floor), a scooter or your own two feet to get there.

 

The road up from Pálli winds first past the virtually abandoned village of EMBORIÓS , where pigs and free-ranging cattle (a major driving hazard) far outnumber people, though the place is slowly being bought up and restored by Athenians and foreigners. New owners are often surprised to discover natural saunas, heated by volcano steam, in the basements of the crumbling houses; at the outskirts of the village there's a signposted public steam bath in a grotto, its entrance outlined in white paint. If you're descending to Pálli from here, an old cobbled way starting at the sharp bend below the sauna offers an attractive short cut of the four-kilometre road, while another kalderími drops from behind To Balkoni tou Emboriou   taverna (sporadically May-Sept, limited menu) to within a quarter-hour's walk of the craters.

NIKIÁ , the large village on the east side of the volcano's caldera, is, with seventy inhabitants, more of a going concern, and its spectacular situation 14km from Mandhráki offers views out to Tílos as well as across the volcanic caldera. There are three places to drink (and, modestly, eat ) here: Porta (summer eves only) and Platia on or near the engagingly round hokhláki plaza, or Nikia , at the entrance to the village. By the bus turnaround area, signs point to the 45-minute trail descending to the crater floor; a few minutes downhill, you can detour briefly to the eyrie-like monastery of Áyios Ioánnis Theológos , which only comes to life at the September 25 festival. To drive directly to the volcanic area you must use the road which veers off just past Emboriós.

However you approach the volcano , a sulphurous stench drifts out to meet you as fields and scrub gradually give way to lifeless, caked powder. The sunken main crater of Stéfanos is extraordinary, a moonscape of grey, brown and sickly yellow; there is another, less-visited double crater (dubbed Polyvótis ) to the west, equally dramatic, with a clear trail leading up to it from the access road. The perimeters of both are pocked with tiny blowholes from which jets of steam puff constantly and around which form little pincushions of pure sulphur crystals. The whole floor of the larger crater seems to hiss, and standing in the middle you can hear something akin to a huge cauldron bubbling away below you. According to legend this is the groaning of Polyvotis, a Titan crushed here by Poseidon under a huge rock torn from Kós. When there are tour groups around, a small, tree-shaded snack bar operates in the centre of the wasteland, and a booth on the access road sporadically charges admission (¬1.50) to the volcanic zone.

Since the 1991 destruction of the old direct kalderími between the volcano and Mandhráki, finding pleasant options for walking back to town requires a bit of imagination and possession of Beate and Jürgen Franke's locally available, GPS-drawn topographical map (free). First choice involves backtracking along the main crater access road for about 1km from the admission booth to find the start of a clear, crudely marked path which passes the volcanic gulch of Káto Lákki and the monastery of Evangelístra on its two-hour-plus course back to the port. You can lengthen the trip by detouring from Evangelístra south to Profítis Ilías , the island's summit, a two-hour round-trip - the route is well marked with cairns or white paint and was cleaned in 1998. An alternative approach to Evangelístra requires returning to Emboriós and leaving from the top of the village, near the cemetery and small castle, on a 45-minute course to the monastery - an enjoyable link, despite haphazard marking and cleaning. From Evangelístra, the onward route to Mandhráki briefly follows the now mostly paved road down before the marked path resumes, handily shortcutting hairpin bends.