Isla Calero (English: Calero Island) is a Costa Rican island, the biggest island in Costa Rica, and the biggest along the San Juan River, which marks the border between Nicaragua and Costa Rica. The island lies between the San Juan (to the north and west), the Río Colorado of Costa Rica (to the south and southeast), and the Caribbean Sea (to the east and northeast). The entire island has an area of 151.6 km2 (58.5 sq mi). On December 16, 2015, The International Court of Justice dictated that the territory in dispute belongs to Costa Rica.