Just north of the Old San Juan district, within the San Juan National Historic Site, lies Castillo San Felipe del Morro, a 16th-century citadel, or fortress.
It is a World Heritage-listed site on the northwestern tip of the islet of San Juan – a perfect spot to keep watch over the Atlantic Ocean and protect Old San Juan and the Bay of San Juan from incoming enemies. Its more recent history includes the American military, which occupied the site from 1898 to 1961.
The citadel, surrounded like it is by an expansive green lawn and the dramatic rocky coast, sits on quite a beautiful spot; the imposing fortress walls create an interesting contrast to the sparkling blue sea. When the wind blows, the lawn that connects the citadel to the town is a popular kite-flying spot.
El Yunque Rainforest is the only tropical rainforest under the protection of the US Forest Service and also the largest nature reserve in densely-populated Puerto Rico. It is situated in the mist-wreathed Luquillo Mountains where year-round precipitation ensures lush, green landscapes and a healthy diversity of animal life. This includes mongooses, non-venomous snakes, the rare Puerto Rican Parrot and the Coqui frog whose distinctive croak provides El Yunque’s soundtrack.
El Portal Rain Forest Center provides a good introduction to the area. There you can pick up a map and set out on well-defined walking trails which will take you past such sights as the La Coca Falls and the observation points of Yokahú Tower and Mount Britton Lookout Tower.
Playa Flamenco is a stunningly scenic beach that is an ideal day trip for those vacationing on Puerto Rico in the Caribbean. Playa Flamenco isn't actually located on the main island of Puerto Rico, though. Instead, you'll have to take a short boat ride to the smaller island of Culebra.
It is worth the trip as Playa Flamenco has a wide, white sand beach that is bordered by clear aqua sea water on one side and bright green hills on the other. High quality food stands line the beach serving a variety of treats, ranging from ice cream and fruit smoothies to ceviche and empanadas. Bathrooms are available onsite and there are also beach chairs and umbrellas you can rent to use for the day. Playa Flamenco also holds remnants of Puerto Rico's military past; on the northern edge of the beach are two old military tanks which are worth an amble along the beach to see.
You don’t have to be a seasoned spelunker to enjoy Río Camuy Cave Park, one of the largest such sites in the world. The caves, sculpted by the underground river from which it derives its name, were only discovered in 1958 and haven’t yet been fully surveyed.
The most accessible part is Cueva Clara. Descending into this subterranean chamber, pierced by shafts of sunlight, lined with luxuriant ferns and echoing with bat screeches, is an unforgettable experience.
Back on ground level you can peer into the enormous Tres Pueblos Sinkhole or set off on a walking trail to explore more of this thickly-forested area.