Culebra is characterized by an irregular topography resulting in a long intricate shoreline. The island is approximately 7 by 5 miles (11 by 8 km). The coast is marked by cliffs, sandy coral beaches and mangrove forests. Inland, the tallest point on the island is Mount Resaca, with an elevation of 650 feet (198 m), followed by Balcón Hill, with an elevation of 541 feet (164.9 m).
Ensenada Honda is the largest harbor on the island and is considered to be the most hurricane secure harbor in the Caribbean. There are also several lagoons on the island, like Corcho, Flamenco, and Zoní. Culebrita Island also has a lagoon called Molino.