Concierge.com's insider take:
Formentera is the smallest of the Balearics, offering visitors mile upon mile of pearl-white sand, crystalline waters, and some of the least developed terrain in Spain. Geologically like a Swiss cheese, the island is formed of pale, porous rock that the sea and elements have carved into dramatic sculptures over millennia, making it a paradise for diving (Vellmarí Formentera, 34-971-312-071; www.vellmari.com). It's worth breaking away from the beach to explore areas like Punta Pedrera, where the sea and wind have carved natural swimming pools into the rock; the Estany des Peix, located on a small lagoon, to see the fishing boats chug in and out; and the lonely, windswept lighthouse La Mola, written about by Jules Verne. Those who prefer their feet on dry land will find that many of the roads remain unpaved, and the preferred method is two-wheeled, by bicycle or moped (Motorent Migjorn; 349-971-32-27-87; www.motorentmigjorn.com). While beaches like Platja Illetes are as packed as any of the resorts on the bigger islands, those willing to explore will find a little piece of paradise to call their own. Head to Es Caló for fresh-caught fish on the beach, or over to Espalmador, a smaller island located 492 feet off the northern tip of Formentera. It has no facilities, but its isolation makes it all the more idyllic. To get there, swim or take a boat.