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. The island regularly picks up 'best in Europe' awards among 75kilometers of sandy shore. Mylopotas is the busiest and the noisiest; a party beach crammed with music bars and fast food cafes. Beyond Mylopotas, it is a different story - beautiful, unspoilt beaches are the norm. Many beaches are remote and relaxed but island travel agents will arrange transport by road or boat.
Chora is the only large settlement on Ios. By day, a dormant village of white cube houses blue domed churches stacked up the hillside and capped by a dozen decaying windmills.
By night, it transmutes into a frenzy of drinking and partying with discos competing to out-decibel each other with techno-pop, heavy metal, punk, rock and even jazz.
The centre is a rash of bars and clubs wrapped around the main square, all very small but together number more than 100.
Many offer a free condom with every cocktail. Local shots called 'bombas' are reputedly spiked with home-made alcohol. 'Headbanger' drinkers don a helmet and get clouted with a hammer. Stylish.
All-night drinking was the norm until locals forced bars to close at 3 am, on weekdays at least, prompting a early-morning stampede to out-of-town dance clubs on the cliffs.
Predictably, taverna menus are seriously unimpressive and the best a visitor can hope for it to queue for a greasy gyros or burger.
The narrow streets keep Chora free of cars and there is plenty to enjoy by day. The church of Panagia Gremiotissa, with beautiful icons, is recognised by a palm tree outside while the windmills, a dozen of them, are a reminder of former days.
The ruins of a medieval castle crowns the hill along with the chapel of Agios Nikolaos and just beneath is Panagia Gremiotissa (Our Lady of the Cliffs), built by Turkish occupiers.
The Archaeological Museum is housed in a yellow neoclassical mansion and has displays of ceramics, Roman artifacts, prehistoric tools and Cycladic figurines.
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 central plaza is packed with shops and the promenade thick with tavernas, cafes and gift shops with a small quay beyond the marina where fishing nets are laid out to dry.
The long sandy beach is to the west of the port, has yet more restaurants and bars and is a popular alternative to the crowded party beach of Mylopotas on the other side of Chora.
Several walking trails start at Yialos leading to sandy beaches at Kolitsani, the hill village of Kambos and beyond that to Skarkos and various ruins of archaeological interest.
An stone flagged path, shaded by overhanging eucalyptus with drinking fountains along the way, leads up to Chora past the domed church of Agios Giorgios hacked into the cliff.
South of Ormos Yialos is the 17th century chapel of Agia Irini with a double set of altars.
On the headland south of Yialos lies Koumpara, or Koubara, an area of small coves and sandy beaches. The main beach is long at about 300 metres and sandy with tavernas and room nearby.
Koumbara's main attraction is the clutch of small coves dotted all around the headland. The odd rock outcrop makes it great for snorkelling and the secluded coves make it popular with naturists.
Koumbara is walkable from Yialos, it takes about 30 minutes, but a regular bus leaves Ormos Yialos on the hour.
Mylopotas is the main beach for Chora has a one kilometre crescent of wide, golden sand that will rival any in the Mediterranean.
In season, non-stop beach music is broadcast countinuously all day as young revellers warm up for a frantic night's drinking at the infamous all-night beach parties.
The bay is awash with cafes and bars with watersports galore to keep the young entertained. A cluster of hotels has sprouted up and two large campsites are aimed at backpackers.
The beach campsites are mini-resorts in themselves with 24-hour bars, pools, tavernas and head-throbbing music.
Farm tracks lead away from the quieter southern end, where unofficial naturism is in favour to a pleasant beach at Kolitsani, mid-way between Chora and Mylopotas.
Buses leave Chora every 15 minutes or so but it is only a 20-minute walk to the beach.
The north coast has a number of attractive beaches but they are widely separated. Many more coves can be found in sheltered bays but are remote and without facilities so they tend to be very quiet. The most beautiful beach of them all is Manganari, now a major target of day trip coaches.
The first beach of any note north of Yialos is at Plakatos, about 13 kilometres away on the northern tip of the island beneath Pano Kambos, the reputed site of Homer's Tomb.
The road runs out after the village of Vouni and a dirt track branches left to Plakatos and right to ancient ruins which islanders claim is the tomb of the great Greek poet Homer.
One popular tale has it that Homer's mother, Clymene, was from Ios, another that the pet, author of the Iliad and the Odyssey, was killed on a visit to Ios after failing to answer a local riddle.
The original graveyard has long since slipped down the earthquake-prone cliff but the ruins are at least Byzantine so a visitor needs some imagination as a companion.
Nevertheless the islanders don't question the connection and on May 15 each year they hold a street festival - Homeria - and carry a flame up here from the port.
The huge sandy beach at Agia Theodoti is about 12 kilometres from Yialos, set in a sheltered bay facing east for breathtaking sunrises over the islet of Ikaklia in the bay.
Local tavernas serve basic, but delicious, food and there are many rooms to let in the area. Being a favoured haunt of wealthy Athenians has helped push up 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 each September 8 to mark a victory by Ios islanders over marauding pirates that once frequented these seas.
The beach is overlooked by the ruins of the 15th century Venetian fortress of Paliokastro, built in 1400 where the remains of the old Venetian town can be seen inside.
A new road has opened up the wild, coarse sand beach at Psathi, the domain of egg-laying loggerhead turtles and of windsurfers.
Psathi is reached down a green and fertile valley of olive and citrus groves, about 18 kilometres from Yialos, which opens out onto a double beach separated by a rock outcrop.
Flat wide sands are backed by a few apartments while a line of tamarisks provides shade on the larger of the beaches. A taverna just above the long beach puts out sunbeds in the summer. More tavernas and rented rooms are found in the nearby village.
The sand is sharp underfoot and shelves steeply in places. The north-facing beach can get windy and this can bring out the surfers in some numbers.
The long sand and pebble beach at Kalamos on the eastern coast, about 16 kilometres from Yialos, is a good alternative to the increasingly popular Manganari to the south.
The local area is a nature reserve and, being relatively remote and well off the tour bus route, remains a peaceful and tranquil haven that attracts only a few visitors.
Enough people arrive to support a small beach cantina that lays out sunbeds in the high season. The clear water and some outlying rocks offer bathers some good snorkelling.
Even more remote coves lie both north and south of Kalamos, all within easy walking distance. A small cove at Plakes is found to the north while, to the south just over the headland, is the hidden cove of Papa, with a small sandy beach but no facilities.
Further south still are 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 kilometres from Yialos.
Manganari has four white-sand beaches necklaced along a coast of crystal clear water. A popular day out for trippers on regular bus excursions the beach has tavernas, bars, cafes and watersports.
Tavernas once noted for their fresh fish are turning to more profitable burgers to those on a break from partying on Mylopotas beach.
Despite the daily visitors, Manganari is big enough to accommodate those seeking peace and quiet and prepared to do a spot of walking. Secluded bays make this an attractive spot for unofficial naturists.
Visitors heading 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 the island travel agents and buses leave from Yialos, Chora and Mylopotas each morning, returning in the late afternoon.
Excursion boats also offer day trips from Ormos Yialos but the boat trip is long, slow and expensive.