Dr. Wily's Robot Manufacturing Plant

Dr. Wily's Robot Manufacturing Plant, known (roughly) as Dr. Wily's giant robot factory (Ｄｒ．ワイリーのロボット大工場) in Japan, named Wily Castle in Mega Man Powered Up, is a robot factory constructed by Dr. Wily in the Pacific. This is his base of operations in the first Mega Man game.

Wily Stage 1
The first stage from Dr. Wily's factory.

Enemies:
 * Big Eye
 * Yellow Devil

Wily Stage 2
Looks like the long mid-path in the concept.

Enemies:
 * Cut Man
 * Copy Robot

Wily Stage 3
Enemies:
 * CWU-01P

Wily Stage 4
The last stage. Yashichi

Enemies:
 * Guts Man
 * Wily Machine No. 1

Other media
Dr. Wily's first base in other media.

Mega Man (Archie Comics)
In Archie's Mega Man comic series, Wily's first fortress has a skull motif.

Mega Man Megamix
is actually a moving fortress.

Elec Man (key character to this base, as it may explode because of him) Rolling Cutter After Elec Man's defeat, Mega Man proceeds and defeats Bomb Man, Fire Man, Ice Man, and Guts Man until he finds Dr. Wily. Yellow Devil MM2 bosses (mainly Quick Man)