Thwomps return in Super Mario 64. This time, though, Thwomps return in a much different fashion, and look more like they did in Super Mario Kart. These Thwomps are square-shaped, dark sky blue-colored with no spikes. They, as before, are impossible to destroy and serve as obstacles throughout the game. Unlike the previous games, Thwomps constantly slam to the ground even when Mario isn't around. This time around, though, Mario can also use Thwomps to his advantage by jumping on top of them to reach higher areas or unreachable points. An interesting feature of the Thwomps in this game is the addition of their voices: a mad grunt. Thwomps are especially featured in Whomp's Fortress, which also introduces new Thwomp-like creatures known as Whomps. A single Thwomp also appears in Tick Tock Clock. There are only three Thwomps in the game, two on the stairs in Whomp's Fortress and one in Tick Tock Clock, at the very top of the stage, and is featured in the mission Stomp on the Thwomp.~Mario Wiki

I would suggest starting at the top and closing of the bottom last.

3D model ripped by alecpike