Secret Places (5)
As soon as you get out of the water and onto the underpass, turn left. Follow the road until it stops. Examine the left wall for a crack. Use an explosive to blow up the crack along the ledge. Jump up to the ledge and walk to the furthest window (far left in the snapshot). Open this window to find the first secret.
There are two secrets in this shot. The first is a hidden door in the bookshelf (left of image). The second is behind a crack in the wall next to the blue access card (right of image).
This secret is in the terminator room. Jump into the yellow/black striped wall to find the secret place.
This secret is hidden behind an operable window. You can see the secret place on the right side of the snapshot. I included the pilons and sewer in the shot so finding the secret would be easier. Once you get inside the secret place, you'll find a door with a crack. Blow up the crack and you'll discover that the last secret connects back to the first secret area.