Christopher Columbus believed that the Earth was shaped like a sphere or a globe. In the 15th century, it was a commonly accepted belief among scholars and navigators that the Earth was round. However, at that time, there was a disagreement about the Earth's size and the distance between Europe and Asia, which influenced Columbus's voyage.
Columbus proposed a westward route to reach Asia, believing that the Earth's circumference was smaller than what was generally believed. He underestimated the size of the Earth and believed that by sailing west from Europe, he could reach Asia more quickly than by traveling eastward. This led to his famous voyages across the Atlantic Ocean and his encounter with the Americas, which he initially thought was part of Asia.
It's important to note that while Columbus's understanding of the Earth's shape was generally accurate, his calculations and assumptions about its size and the location of Asia were incorrect. His voyages, however, played a crucial role in the European exploration and eventual colonization of the Americas.