Level 21: My Own Private Thermopylae
Upon arrival there are three possible paths.

There are three switches and a re-charger, activate them to bring up three sets of stairs. Begin by taking the stairs on the far left.

Return below and take the far right hand stairs. The will lead to a long room with water pools and other interesting constructs. On the left hand side there is this curious contraption. Go through it and take the platform to the top.

On the top level you will see this waterfall - don't try to swim up it - there's nothing in there. But to your right there's the first of the A.I. activation sites - proceed...

This is the first A.I. site. You know the drill, hit the switch and enjoy the lights : )

Now, head back and take the last of the three stairs. As you reach the top of them look to your left - aha, an AR. You might as well jump down to grab it. But beware, you are not alone.

After retrieving the AR there's a passage way leading to a platform. Use this platform to head higher up.

As you reach the top you will eventually come to this room. The BOBs here will be busy shortly with a few Aliens of their own. Help them out (the BOBs, that is).

If you follow the path straight on you'll come to a plateau. From this plateau you can see a spiraling pathway - jump to it.

Follow the pathway around. This may involve jumping from ledge to ledge.

Another A.I. awaits... but remember to kill anything in your path.

Once the A.I. is activated head back to the first terminal.