Check out the whole sequence of screenshots.
Don't waste any time climbing the front stairs to Satan's huge mansion, rockets are already flying at you from both sides! You open the huge arched door revealing a pair of curved staircases. There's no time to admire the architecture though, you've already been hit by shotgun fire!
This wad is for the original Doom v1.666. It supports single player, deathmatch, and cooperative play. It has multiple skill levels and secrets. All the secrets have clues; you never have to run along walls hitting the space bar, that's boring. The level includes all the weapons, but you have to fight your way through to them. On the highest skill level you'll have to be clever to deal with the two rocket-firing cyberdemons and four chain-gun-wielding spiders! Don't worry, it can be done, and to prove it, I've included a v1.666 lmp of me completely solving the level on the hardest skill level.