What are some secret places here?

There are only two secret places, and both involve finding the Control Room
of the Enterprise.

(1) Near the end of the level, go up the escalators.

In that big, central section, you'll find the entrance in there.

Look for a hidden switch.

Not too far away from the First-Aid compartment, there's a door that will
open to reveal an alcove.

Inside is some steroids and a switch.

If you hit that switch, a wall will lower on the other side of the big room.

The object is to hit the switch, and run to the newly-opened wall.

I found that the best way to do this was stand far away from the switch,
shoot it with a Shotgun, then run to the hidden passage.

Go down the elevator in the passage to get to the Bridge.

Now, there's a hidden room here, too.

(2) Head for the adjacent room with the fishtank in it.