What other neat places are there?

Hint 1 of 11:

(1) At the beginning of the level, there's a switch that you can hit to lower
the electric chair, revealing some stuff.

Hint 2 of 11:

(2) One really cool place is near the beginning, in the chapel.

Hint 3 of 11:

Go up to that weird picture-like thing near the windows, and press the Space
Bar.

Hint 4 of 11:

Everything should turn red.

Hint 5 of 11:

Go in, and you'll not only find a Chaingun, but you'll find the Space Marine
from DOOM!

Hint 6 of 11:

(3) Also in the church, go to the back, and stand between the two doors.