Mental Institution is the 41st and last level in Serious Sam 2.
Sam finally reaches the outskirts that lead to the Mental Institution, Mental's hideout. However, the area is rigged with multiple large metal walls that force Sam to fight off large amounts of enemies before he can get closer to the Institution.
After fighting off an incredible amount of enemies, including 10+ T-Mechs, Giant Spiders and The Generals, Sam finally reaches the base of the Mental Institution. However, before he can access it, the pyramid springs to life and starts launching Fatso and Seagull Fighters at Sam, along with bombarding him with fireballs and Cannonballs. However, thanks to a powerful CH-181 Hover Bike that appeared when the pyramid sprang to life, he manages to defeat the Institution, which gives him access to Mental's residence.
1. In the third area (the right-angle/elbow-shaped arena that has Kleer Skeletons, Rhino Cybertoys and ScorpSoldiers coming through three garages), wait until you see a large The General coming towards you. Now, move to the opposite end of the area (where the Super Health, Super Armor and Backpack were earlier and kill The General. When he's down, the wall on the right will go down. As soon as you enter the next area, turn and walk left. After walking for a second, you'll see an opening on your left. Go inside it and three Serious Bombs and a CH-181 Hover Bike will appear. Get into the Hover Bike to register the secret.