Riccioli is a large lunar impact crater located near the western limb. It lies just to the northwest of the even larger and more prominent crater Grimaldi. To the southwest are the craters Hartwig and Schlüter that lie on the northeastern edge of Montes Cordillera, the ring-shaped range that surrounds Mare Orientale. Due to its location, Riccioli appears strongly foreshortened from the earth and is viewed almost from the side. (wikipedia entry)
A crater is a circular depression likely created by an impact event. On the Moon they are named after deceased scientists, polar explorers, astronauts or cosmonauts.