It's the biggest in the Caribbean and it goes on for weeks—if you count activity in the Mas (masquerade band) Camps, make that all year. Preparation begins in earnest sometime before Christmas (depending upon when Easter and Ash Wednesday fall) with steel drum (pan) band practices and warm-up parties and events. The Chutney Soca Monarch Competition—a face-off between players of East Indian chutney music combined with calypso and soca—takes place early in the season and is great to see. Throughout the season you'll find 20 or so calypso tents open most nights—try The All-Stars and Spektakula. There are daily events closer to Mardi Gras, with the selection of National Pan and Junior Calypso champs and the Carnival King and Queen contests being highlights. Carnival proper kicks off on the Sunday night before Ash Wednesday with Dimanche Gras, which segues into J'Ouvert at 4 am Monday, when everyone gets covered in dyed mud—each parade band is smeared in a different color—and hits the streets. The processions of bands and people in costume eventually culminates in Queen's Park Savannah, Port of Spain.

A mere half hour northwest from Port of Spain's bustling business center is the peninsula of Chaguaramas, a yacht and recreation haven in the cadre of a national park and quiet village. Watersports enthusiasts are well catered for with plenty of parasailing, jet skiing, windsurfing, and Chinese dragon boating. There's a nine-hole golf course cradled between mountains, hiking trails, mountain biking, plus a couple of beaches. Escape further by catching a boat to offshore islands where you can descend into the depths of a limestone cave, have a beach picnic, visit a lighthouse, and bird watch.

Trinidad's proximity to South America, to which it was once joined, plus the diversity of its habitats, have given it by far the most species of flora and fauna in the West Indies. The Northern Range—3,000 feet high at its tallest peak, El Cerro del Aripo—is mostly covered in tropical rain forest. It provides especially good vantage points for catching sight of some of the 108 species of mammals, 430 birds, 55 reptiles, 25 amphibians, and 617 butterflies (and a few tarantulas) who make their home on Trinidad. Well-marked trails through the rain forest lead off from the Asa Wright Nature Centre. If you're more in the mood for bushwhacking, leaders from The Pathmaster—an organization of professional rain-forest guides—will take you on day-long or week-long excursions through tropical jungles and along the Northern Range (www.thepathmaster.com). For a simple bird-watching trip, you can take a boat out with Nanan's Tours on Caroni Marsh to see the hundreds of scarlet ibis come home to roost at sunset—an incredible sight (868-645-1305; www.nananecotours.com).

Trinidad's Northern Range—where El Cerro del Aripo is the island's tallest peak at 3,000 feet high—is the backdrop to the island's Caribbean shoreline. You'll find beautiful beaches, gnarly surfing, and, during the summer season, mammoth leatherback turtles coming ashore to night-nest. Closest to Port of Spain, Maracas Bay's wide stretch of tawny sands along the north shore is most popular. It's also known for its "shark and bake" shacks. Nearby, Las Cuevas and Blanchisseuse bays also make spectacular beach destinations.

Turn-of-the-century (19th to 20th, that is) colonial mansions line the center of Port of Spain's universe—the vast grassland Queen's Park Savannah, site of Carnival's culmination each year. There's a free National Museum & Art Gallery on one side of the park, and a zoo, botanical gardens, and the President's home on the other. Also lining the road are various flatbed trucks piled with young coconuts that vendors render into cool beverages with a few machete swipes and a straw.

Tobago is well loved for its beaches, diving, lush countryside, and bird watching. The islands' best beaches line the Caribbean Sea, from the vendor-lined Store Bay, Pigeon Point, and Sandy Point near the airport on the western tip, to the village of Castara and gorgeous Englishman's Bay on the north coast. Take a boat from Buccoo to the Nylon Pool—on her honeymoon, Princess Margaret announced the color was so crazy blue it looked like nylon, and the name stuck. Bird-lovers and scuba divers head to the northeast coast, anchored by the village of Speyside and its handful of guesthouses and resorts. Facing the Atlantic Ocean, the coastline here is rockier, with rougher waves. Little Tobago Island lies offshore, and the waters in between draw divers for their Volkswagen-sized brain coral and population of manta rays. If you want to explore off coast or off the beaten track through the rain forests on the mainland, it's best to hire a guide: Tobago Now Tourism offers many different day-trip excursions. Tobago's hilly capital, Scarborough, can be walked from end to end in an hour. There are busy docks and a daily market, stores, and bars, but you feel it's all more for the residents than the visitors—though you're certainly welcome to share. At dusk, climb up to Fort King George to take in the total dearth of neon and high-rises. The Tobago Museum on site is worth a visit during weekdays.

The second half of July showcases what's endearingly enduring about Tobago history and culture, with daily events and festivities throughout the island. Highlights include the Old Time Tobago Wedding in Moriah, the Goat & Crab Races at Buccoo Bay, the Ole Time Carnival and Mas Parade in Plymouth, and the Food Fair in Scarborough.

Trinidad's 430 species of rare and exotic birds—including the scarlet ibis and the oilbird—draw a big binoculars crowd. Caroni Swamp Bird Sanctuary, a short drive from Port of Spain, is the place to spot flocks of ibis. They come to roost in the swamp's rookeries around sunset; 4 pm tours with Nanan's Bird Sanctuary Tours take you to watch them swoop in by the flock-full. The island's rain forest harbors a host of birds and other animals, including agouti, iguanas, howler monkeys, and armadillos. Asa Wright Nature Center allows easy access into the mountain forest and, along with Aripo Caves, is a prime location for spotting cave-dwelling oilbirds.