Bullialdus (Moon)

Named after Boulliau, Ismael Bullialdus - French astronomer (1605-1694).

Bullialdus is a lunar impact crater located in the western part of the Mare Nubium. To the north by north-west is the broken-rimmed and lava-flooded crater Lubiniezky. South-west lies the smaller crater König. The isolated location of this crater serves to highlight its well-formed shape. (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.