This center can be found behind a door inside the Testing Ground Control Center on Level 4 in Wizardry: Proving Grounds of the Mad Overlord (12E/15N). What awaits the party of cocky adventurers is one of the toughest fights in the game: A High Ninja, accompanied by a pair each of Lvl 7 Fighters, Lvl 7 Mages and High Priests. Even much more experienced parties accustomed to Werdna's lair in Level 10 might still get into trouble as the spellcasters may stun the player's mages or silence them with Montino. The High Ninja, needless to say, is very quick in decapitating a character.
Sometimes, it is possible to avoid this tough fight, when the monsters turn out to be friendly. Simply decline to attack them and proceed into the chamber. You won't get the loot, of course.
Two one-way doors lead further south, each accompanied with an atmospheric description. Eventually, the party will hear the voice of Trebor who congratulates them to their achievement. He then explains the main quest to the party. The characters should seek the evil wizard Werdna in the levels below, slay him and return the stolen amulet to Trebor. Yes, the party is actually hired to assassinate Werdna.