In this next area, you'll notice a minecart is stuck under a gate. Slip through the minecart on the side and run to the end. Jump down into the rubble below the tracks and run into the small cave. Pick up the food. You'll need to bring the food to Trico by tossing up the ruins (aim for the squares with the blue shards on them). Once you get it up, bring the food to Trico, now he will listen to you.
Go back through and pull the minecart far enough back so you can jump on the ledge. Pull the lever and Trico will push the remaining cart as it comes though. Once Trico is through navigate through the dark corridor at the end of the hall. Use Trico's glowing eyes for light. Once at the end, hop on Trico's back and command it to leap out.
Once outside you'll see a bunch of spiral towers with stained glass eyes. Hop on Trico's back and hold on as he jumps. He'll stop at the first glass eye. Climb down his tail and navigate the tightropes across the tower until you reach the first glass eye. Drop it.
Once you drop the eye, shimmy down the chain link and jump onto Trico's back. Again, command him to jump and he will do so until he reaches the second glass eye. Climb down and shimmy on the side of the spiral tower, through the crack, onto the beam that's holding the glass. Drop the glass…
Surprise! It falls and knocks you loose. Wait for Trico to run below, and let go, calling his name as you do so so he catches you. Climb up his tail and command him to jump further.