The geography of Puerto Rico consists of an archipelago located between the Caribbean Sea and the North Atlantic Ocean, east of the Dominican Republic and west of the Virgin Islands.The main island of Puerto Rico is the smallest and most eastern of the Greater Antilles.With an area of 3,515 square miles (9,104 km 2), it is the third largest island in the United States and the 82nd largest island in the world.he archipelago of Culebra, located east of Puerto Rico, north of Vieques, and west of the Virgin Islands, is composed of the main island of Culebra and 28 uninhabited islets. Mainly mountainous, the island of Culebra possesses renowned beaches.