What lands did Columbus believe lay on only about 4000 mile?

Columbus believed that Asia, specifically the East Indies, lay just about 4,000 miles west of Europe across the Atlantic Ocean. He underestimated the Earth's circumference and the distance to Asia, thinking he could reach it by sailing westward. Instead, he encountered the islands of the Caribbean, which were part of the Americas, not Asia. This miscalculation was pivotal in the history of exploration and the subsequent encounters between Europe and the Americas.