Byrgius is a lunar crater located near the limb. As a result, Byrgius appears strongly oval in form due to foreshortening. To the northwest is the nearly ruined crater Lamarck. The rim is worn and eroded, with Byrgius A overlying the eastern rim and Byrgius D lying across the northwest. (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.
