Dominica's second largest town, down-at-the-heels PORTSMOUTH, has a picturesque location along Prince Rupert's Bay but functions mostly as a university centre. Originally envisioned as the island's capital, plans went awry when the swampy, mosquito-infested environs couldn't be tamed. While there's not much to keep you in town, the Indian River on the southern outskirts is worth a visit for the boat trips upriver through the marshy backwaters that stymied developers. Sightings of blue herons and crabs are common, and you'll stop for drinks at an alfresco jungle bar. Park Service representatives take visitors upstream from the river's mouth - the best guide goes by the name of Macaroni. Portsmouth's other noteworthy attraction is the twin-peaked Cabrits National Park, a grassy headland jutting out into the Caribbean Sea 1.5 miles north of town. While the park encompasses the island's largest swamp and the shoals and coral reefs of nearby Douglas Bay , the main point of interest is the ruins of Fort Shirley . Built between 1770 and 1815 mostly by the British to defend against the French, and completed by the latter when they took control of the island, the fort became a mammoth complex that ultimately was abandoned in 1854. The ruins closest to the entrance have since been restored, while those further afield remain cloaked in jungle overgrowth.