A tiny archipelago sitting just a mile off the Costa Brava, the Illes Medes boast no luxury hotels, no flashy bars and no sandy beaches. Just one lone lighthouse advertises the presence of the archipelago's seven islets, some of which are merely bumps barely big enough to spread a towel on. At first glance, there doesn't seem like much to draw you here, but stick around and you'll discover that what the Illes Medes lack in size and neon lights they make up for in unparalleled natural beauty.

The islets are known mainly as a diving destination, though non-divers can enjoy them too by going snorkelling or boating. As the natural habitat of some 1,350 classifications of marine life, the waters around the Illes Medes rank as one of the top scuba diving spots in the Mediterranean and are the unparalleled diving paradise of the Costa Brava. The area is so important that it has been declared a marine reserve and is strictly protected, with limits on the number of divers that can visit the site and a complete ban on fishing.

L'Estarit, a lively Costa Brava resort and the town nearest to the seven islets, is nearly within swimming distance, but the Illes Medes feel like they're a world away from the bustle of the coastal town. While the hum of splashing children and ice cream vendors dominates in L'Estartit, quiet descends on the islands, where the only noises you hear are the waves of the Mediterranean, the calls of the seagulls and the occasional purr of a motorboat. Of course, if the quiet gets to be too much, it's only a 5-minute boat ride back to the beach buzz.

Geographically the islets form part of the Montgrí massif, a rough-looking rock formation that's part of reason this stretch of coastline was dubbed the Costa Brava, or "Rugged Coast". Over time, erosion carved out the irregular forms that we recognize today as the Illes Medes. The islets are scattered around the mouth of the organic-rich River Ter, the source of a constant stream of food that nourishes lush marine plants and attracts dozens of marine species including octopus, bream, lobster and star fish. Occasionally dolphins, whale sharks or bigger fish like Blue Marlins appear as well.

"The illes are beautiful," said Peter Lane, owner of Calypso Diving and a diver who's been exploring these waters for 35 years. "There's a massive fish population not found anywhere else on the Costa Brava. If you come you'll see immediately why this area is so well thought of among divers."

Inma Ros, scuba diver and director of Estación Nautic, a public office specialized in local coastal tourism, said the Illes are considered one of the best diving areas in the whole of the Mediterranean. "You're guaranteed to see a huge variety of fish in addition to coral, plants… the species living here are infinite," she said.

So many species make this their home in part because of the variety of land formations here. Crustaceans nestle along the rocky coasts, while starfish lie on the shallow sandy bottom near the beach, and further out coral reefs provide excellent haunts for colourful fish. Underwater tunnels and caves are the hiding places for larger fish.

So much variety means that there are dives for all styles. Beginners diving no more than 10 meters deep will be able to spot lobsters and octopuses, while more experienced divers can head out to the rich coral landscapes that thrive in deeper, cooler waters. Expert divers can explore the caves dug by time out of the rock massif. Caves like La Vaca ("The Cow") feature a series of tunnels that house marine plants and fish. The mouth of La Vaca is well-lit and ideal for photography, while its inner reaches are a mysteriously dark hole that guarantees a thrill.
There is even a wrecked ship nearby, which is one of divers' favourite spots to explore. The Reggio Messina, intentionally sunk in 1991, is a short boat ride from the islands and is the largest dive-able ship on the coast here.

Diving is the Illes Medes' claim to fame, but non-divers don't have to miss out on the fun. Glass-bottom boats make tours of the area, letting you get a peek at the abundant life under the water. On the dry land of the islands, unique birds including the cattle egret, the night heron and yellow-legged gulls have made their home, making this area popular with bird watchers. Those wanting to test the diving waters can do "try dives," short, shallow-water dives that are supervised by an instructor and intended to give a feel for scuba diving. You could also snorkel around the shore; many scuba outfitters also rent snorkel gear.

These unassuming islets hide a fascinating history. As far back as 500 BC the ancient Greeks were passing nearby, and more than one of their wrecked ships has been found in the area. Human bones found on one of the larger islands suggest that there was a small settlement here during that time as well. Later, in the middle ages, the islands became a hideout for pirates who took advantage of the region's busy marine trade to attack and rob ships. The pirates used the Illes Medes as a base for raiding the coast. Finally, in the 15th century, the king ordered a fort built on the Meda Gran, one of the larger islets, and filled it with knights to defend the shipping trade. The pirates were not intimidated and attacked the fort time and time again, until at last the knights abandoned it. A century later, the fort and a chunk of the islet beneath it crumbled into the sea.

The days of adventure were not yet finished on the Illes Medes; in the 1700s the Meda Gran was used as a military prison, and a small base was set up. The base would stay until 1890, when it was finally abandoned. The island was inhabited until 1930, when the last resident - the lighthouse keeper - finally left for the mainland. These days there is not so much as a campground on these small, protected islets; L'Estartit serves as the home base for those setting out to explore the islands.

The town of L'Estartit is a charming place worth visiting even if you don't plan to dive. Sitting at the base of the Montgrí massif with the sparkling Mediterranean spread out before it, the setting is unbeatable. The town's other offerings, like sailboat rental, windsurfing or just sun-soaking on the white, sandy beaches, entertain the non-divers, and a wide variety of hotels, campsites and restaurants keep you eating well and sleeping soundly.

IF YOU GO:
• When to go: Most scuba outfitters are open year-round, but the high season is, predictably, May through late September. This time of year the water is warm and generally calm, and all of L'Estartit's restaurants and hotels are open.
• Reputable diving outfitters and instructors abound in L'Estartit. Most offer similar services: a quick boat trip to the islands and diving off the boat. Local outfitters include El Rei del Mar (www.rei-del-mar.com) and Unisub Estartit (www.unisub.es).
• Single dives take anywhere from 40 minutes to an hour, depending on the depth and how quickly you consume the air in your tank. Expect them to cost around €25 (equipment included). Speciality dives like night dives or first-timers' try dives (shallow dives in the close company of an instructor) may be priced differently. Certification courses are available starting at €350 and may be offered over a week or two weekends.
• Get more information on L'Estartit and the Illes Medes at www.islasmedas.com or www.enestartit.com. Or contact the Estacio Nautica, the local tourist office, at 972 750 699. They can recommend local outfitters and instructors, and will also be able to help with lodging, transportation and activity options.