After dragging the dead soldier off the trapdoor, and returning to the DEAD-END ALLEY WITH THE CRAWLSPACE, as shown in the previous section, climb onto the block in the corner and crawl backwards into the small opening.

Drop down into the passageway below...

...and follow it...

...to a room with a lever and a small medipack. (Lara won't target the rat that scuttles across the floor, so we don't count it as an enemy.)

Use the lever to open a trapdoor above. This will work only if you've dragged the dead soldier's body off the grate, as described in the last section.

Grab the medipack if you didn't already and climb up through the opening.

Turn around and jump straight up to grab the edge of the crawlspace.

Pull up and crawl forward until Lara can stand.

Follow the passageway up to a second lever.

Use it...

...to open a door above the grate in the ceiling. You can't get there from here, so return to the DEAD-END ALLEY WITH THE CRAWLSPACE, where you left the motorcycle, either through the crawlspaces the way you came or via the streets if you destroyed the machine guns.

[City of the Dead Walkthrough]