The 316-acre reserve on a headland north of Fajardo is owned by the nonprofit Conservation Trust of Puerto Rico. You ride in open-air trolleys and wander down boardwalks through seven ecosystems, including lagoons, mangrove swamps, and dry-forest areas. Green iguanas skitter across paths, and guides identify other endangered species. A half-hour hike down a wooden walkway brings you to the mangrove-lined Laguna Grande, where bioluminescent microorganisms glow at night. The restored Fajardo Lighthouse is the final stop on the tour; its Spanish-colonial tower has been in operation since 1882, making it Puerto Rico's second-oldest lighthouse. The first floor houses ecological displays, and a winding staircase leads to an observation deck. The only way to see the reserve is on a guided tour; reservations are required through the trust website.