IOS sits in the southern part of the central Cyclades group, just south of the Greek islands of Naxos and Paros.
Once considered the party capital of the Med, the glory days of Ios have faded as the island lost out to more nakedly aggressive beach party resorts as Faliraki, on Rhodes, and Ayia Napa, on Cyprus.
Nevertheless, Ios remains a major hedonist outpost where sun, sex and sin await youngsters from all over the world. They have been sailing in for decades for the annual beach bar binge.
Once neck-and-neck with Faliraki for the Greek islands' top party island title, Ios is considerably tamer today than it once was.
Long-suffering slanders have worked hard to cast off the island's loutish reputation. Brassed off locals, annoyed at the booze-sodden behaviour of young visitors, imposed a 3am weekday shutdown on clubs.
Some will dub Ios a party island and nothing else, but the clubs, bars and discos are totally confined to the island capital port, Chora village on the hill above it and Mylopotas beach beyond.
Outside the booze happy capital there lies a classic Greek island with some simply wonderful beaches and timeless villages easily reached on well-paved island roads..
If you are not the party type then avoid the capital and head north or east for peace and tranquillity on some of the best Greek island beaches you will ever come across.
In addition to the notorious nightlife, Ios can boast beaches that are the envy of many. Ios regularly pick up best beaches in Europe awards and boasts 75km of sandy beaches although few are developed as tourist beaches. Mylopotas beach is the busiest and the noisiest; a party beach crammed with music bars and fast food cafes and blasted by loud music. Away from Mylopotas, it is a different story - beautiful, unspoilt beaches are the norm, with Manganari in the south-east considered the best and the official nudist beach of Koumbara, to the west of Chora, a close second. The remaining Ios beaches are strung along the north and east coasts and tend to be quiet and relaxed. Ios island travel agents will arrange transport to more remote stretches of sand and offer sailing trips around Ios and to nearby islets.
CHORA is the only town on Ios. By day it is a dormant village of white cube houses stacked up the hillside, dotted with the blue domes of churches and capped by a dozen decaying windmills.
By night, and especially after midnight, Chora transmutes into a frenzy of drinking, partying and vomiting as competing discos and bars out-decibel each other with techno-pop, heavy metal, punk, rock and even jazz.
The Chora centre is now little more than a rash of bars and clubs wrapped around the main square. The bars are very small but together they must total more than 100.
Most offer cheap booze while some offer a free condom with every cocktail. If the booze is cheap, so is the quality. Local drinks known as 'bombas' are reputedly spiked with home-made alcohol. For 'headbangers' the drinker dons a helmet and is clouted with a hammer - stylish then.
All-night drinking was the norm until the locals could stand no more and forced bars to close at 3 am, on weekdays at least, prompting a early-morning stampede to out-of-town dance clubs located on the cliffs.
Predictably, food is not top of any partygoers' list - just something to soak up the alcohol - and Chora taverna menus are seriously unimpressive. The best you can do is queue for a greasy gyros or burger.
The narrow Chora streets make the town inaccessible to vehicles and for those out and about in the daytime there is plenty to enjoy.
The main church of Panagia Gremiotissa with its beautiful icons, easily recognised by the palm tree outside while the Chora windmills, a dozen of them, now tarted up for the tourists, are a reminder of former days. The ruins of a medieval castle sits on the hilltop as well as the chapel of Agios Nikolaos (one of 400 or so on Ios) and under the castle is Panagia Gremiotissa (Our Lady of the Cliffs), built when Turks occupied Ios.
The Archaeological Museum of Ios is housed in a yellow neoclassical mansion with displays of ceramics, Roman artifacts, prehistoric tools and Cycladic figurines. It opens 8am to 2pm, except Monday.
Below the Chora is the port area of ORMOS, YIALOS or GIALOS, one of the biggest natural harbours in the Aegean and the first glimpse most visitors get of the island.
The main Yialos plaza is packed with shops and travel agents while the promenade is thick with tavernas and cafes as well as gift shops. There is a small fishing boat quay at the end of the marina where the men still mend their nets on the quayside.
To the south is the 17th century chapel of Agia Irini with its double set of altars. The long sandy beach of Yialos is to the right of the port and there are yet more restaurants, bars and cafes.
The beach is long and sandy with sunbeds and water sports. It is a good alternative to the more crowded Mylopotas which is on the other side of the headland below Chora and where most of the youngsters hang out.
Various walking trails start at Yialos. Paths from here lead here to remote sandy beaches at Kolitsani, the hill village of Kambos and beyond that, at Skarkos, are various ruins of archaeological interest.
An old stone flagged path leads up to Chora past the domed church of Agios Giorgios hacked into the cliff. The path may be steep but there is pleasant shade from overhanging eucalyptus and drinking fountains along the way.
On the headland south of Yialos is KOUMBARA or KOUBARA, an area of small coves and sandy beaches. The main beach is long (about 300m) and sandy with beach tavernas and room nearby.
But Koumbara's main attraction are the clutch of small and delightful sandy coves to be explored on foot around the headland. The odd outcrop of rock also makes this an ideal place for snorkeling and the many secluded coves make it a favourite with naturists.
Koumbara is walkable from Yialos (about 30 minutes) but there is a regular bus on the hour that takes about 5 minutes.
MILOPOTAS or MYLOPOTAS is the main beach for Chora has a 1km crescent of wide, golden sand that is said to rival any in the Mediterranean - if you can find somewhere to enjoy it.
In season Mylopotas heaves with tan-oiled bodies during the day, while its all-night beach parties are infamous. Non-stop beach music is broadcast loud and clear all day for the benefit of young revellers warming up for a frantic night's drinking.
A cluster of upmarket hotels has sprouted up at the head of Mylopotas beach and there are two large campsites for backpackers. Mylopotas bay is awash with cafes, bars and restaurants which are open day and night, there are watersports galore and all the usual sunbeds and parasols.
Beach camp sites at Mylopotas are mini-resorts in themselves with 24-hour bars, swimming pools, restaurant and head-throbbing loudspeakers. But at least Mylopotas beach is long enough to escape the worst of the noise.
Farm tracks take you to the quieter southern end where unofficial naturism is in favour. There is a pleasant beach at KOLITSANI, mid-way between Chora and Mylopotas, accessible by a path, if you want to escape the worst of the crowds.
Buses leave Chora every 15 minutes or so but it is only a 20 minutes walk anyway so by the time you have waited for the next crowded bus you can be there on foot.
The north coast of Ios has a number of attractive beaches but they are all widely separated. Many more coves can be found in sheltered bays and are quite remote, without facilities, so they tend to be very quiet. The most neautiful of them all is Manganari, now a major target of day trip coaches, although it is big enough to take the numbers without seeming too crowded.
The first beach of any note north of Yialos is found at PLAKATO or PLAKATOS, more north-west than north and about 13km from Yialos. It sits at the northern tip of the island beneath PANO KAMBOS, the reputed site of Homer's Tomb.
The asphalt runs out after the village of Vouni and a dirt track branches left to Plakato and right to ancient ruins, where tradition has it that the poet is buried.
One tale has it that Homer's mother, Clymene was from Ios, another that he was killed after failing to answer a local riddle.
Anyway, the original graveyard has long since slipped down the earthquake-prone cliff and what remains is said to be Byzantine anyway so a trip here requires good footwear and a good imagination.
Nevertheless the islanders are very proud of the connection and on May 15 each year they hold a festival - Homeria - when and a flame is carried up here from the port.
The huge sandy beach at AGIA THEODOTI is about 12km from Yialos, set in a sheltered bay facing east for those early enough to catch a breathtaking sunrise over the islet of Ikaklia in the bay.
Local tavernas serve basic but delicious food and there are many rooms to let in the Agia Theodoti area. A favoured haunt of wealthy Athenians this has helped push up local prices so don't expect a cheap meal.
Sand shelves gently into the sea which is usually limpidly calm. Nearby is the 16th century church of Agia Theodoti, the oldest on the island, that gives the bay its name.
A celebration is held at Agia Theodoti on September 8 each year to mark a famous victory by Ios islanders over the marauding pirates that once frequented these seas.
Agia Theodoti resort is also overlooked by the ruins of the 15th century Venetian fortress of PALIOKASTRO. It was built in 1400 by the Venetian Duke Marco Crispi and the remains of the old Venetian town can still be seen inside.
A new road has opened up the coarse sand beach at PSATHI which was once the domain of egg-laying loggerhead turtles but increasingly seems the main destination of mating windsurfers.
Psathi resort is reached through a lovely green and fertile valley of olive and citrus groves (in spring at least, the landscape is far less attractive in the summer), about 20km from Yialos.
Flat wide sands are backed by a few tavernas and apartments. Doubtless a beautiful spot, but the sand is quite sharp underfoot and Psathi beach is north-facing so it can collect a fair amount of rubbish in the prevailing winds.
The sand at Psathi can shelve pretty steeply into the sea in places so care must be taken and there are few sunbeds or other facilities.
On windy days the sea swells can attract scores of windsurfers to Psathi bay. To get there follow the signs from Agia Theodoti.
A long sand and pebble beach at KALAMOS on the eastern coast, about 16km from Yialos, is said to offer a good alternative to those who tire of the increasingly popular Manganari to the south.
The area around the long and beautiful Kalamos beach is a nature reserve and, being relatively remote and off the tour bus route, a peaceful haven that you are likely to enjoy with few other visitors.
There are enough visitors to Kalamos to support a beach cantina that supplies sunbeds and umbrellas. Waters are clear and with outlying rocks to give good snorkeling.
If you prefer even fewer crowds there are even more remote beaches both north and south of Kalamos within easy walking distance. North lies a small cove at PLAKES and to the south, just over the headland, is the hidden cove of PAPA.
Further south still TRIS ELIKES, a trio of beautiful secluded beaches, accessible only on foot.
One of the most romantic areas of Ios, MANGANARI sits on the south-east coast about 23 km from Yialos.
Manganari is actually four beautiful white sand beaches necklaced along a coast of crystal clear water. There are beach tavernas, bars, cafes and watersports and this is now a very popular day out for trippers on the regular bus excursions. Then again Manganari is still big enough to find peace and quiet if you are prepared to do a spot of walking. The secluded bays make the place attractive for unofficial naturists.
Manganari tavernas were noted for their fresh fish menus but are now turning to more profitable burgers to supply the visiting youngsters who increasingly turn out of the coaches while on a break from partying on Mylopotas beach.
Too get there by car drive through Mylopotas and take the hill road turning right before Kalamos monastery. Bus excursions to Manganari can be booked in all travel agencies and buses leave from Yialos, Chora and Mylopotas, returning in the afternoon.
You can also catch a water taxi from Yialos - slow and expensive.