Proto Man's Castle

Proto Man's Castle, known as Blues Castle (プルース城) in Japan, is a fortress that appears in Mega Man 5 after the defeat of all eight Robot Masters. The castle consists of four parts, each part being a stage Mega Man must go through to save Dr. Light from Proto Man. Despite the name, it wasn't actually built by Proto Man, instead being built by Dr. Wily as a secondary base used by the four Dark Men, one of them being a Proto Man impostor created by Wily to frame Proto Man. In the last stage, the real Proto Man appeared and revealed that the other is an impostor.