Tucked away in the gorgeous backroads and byways of northwestern Puerto Rico is the largest radio telescope in the world. The facility is operated by Cornell University and word has it this is where the US government monitors extra-terrestrial life, but even if you want to steer well clear of X-ophilia, you can enjoy the excellent science and space interactive museum and the impressive 305m diameter (1000ft) telescope itself.

Since the US Navy stopped using the archipelago for target practice in the mid-1970s, this cluster of 24 scrubby islands 35km (22mi) off the coast of eastern Puerto Rico has experienced a more beneficial boom. The definition of traffic here is still sharing the road with another vehicle, but more and more travelers and locals are beginning to appreciate the charms of this sleepy backwater, drawn by its beautiful beaches and the fantastic snorkeling and diving offered by its coral reefs.Culebra itself measures a modest 11km by 6km (7mi by 4mi), but it dominates the archipelago. The island's undistinguished main town, Dewey, contains most of the area's 2000 souls. Travelers should head to the northern coast to Flamenco Beach or to nearby Playa Resaca. The Culebra National Wildlife Reserve encompasses parts of Culebra and the outlying islands, protecting significant seabird colonies and turtle-nesting sites. You can visit the surrounding cays by chatting up the local fishermen or by arranging dives through local operators. There's a ferry to Dewey from Fajardo that takes an hour or so, and air connections to Culebra from both Fajardo and San Juan.

There's no town to speak of on this lovely stretch sandwiched between the coast and well-forested mountains, but this low-key beachy settlement is a good base if you want to go bushwalking, horseback riding or simply take in a few sunsets. Get local advice before you plunge into the surf - some stretches of beach here are treacherous. Patillas is on Puerto Rico's southeastern coast about an hour's drive east of Ponce.

This eco-savvy town with surf and bay beaches is well-colonised by American wave addicts and Puerto Rican families. The surf's up from October to April, when if you're not sun-bronzed and hair-bleached, you're just not cutting it. Non-watery attractions include El Faro (lighthouse), where there's a small maritime museum and whale- and dolphin-spotting platforms. From here you can also sneak a peak at the spooky dome of Latin America's first nuclear plant, operational between 1964 and '74 and now nestled innocently among palm trees.