There is a metal ring on the ceiling, so grapple it and swing to the small square ledge with the Treasure (20/28) on the right. (You can also ignore the ring and jump directly to the ledge.) Get it and jump to grab the handhold on the pillar.

Traverse to the left around the three corners and release to grab the narrow ledge below. Traverse to the left, almost to the end, and pull up on the ledge.

Jump forward to land on top of the vertical column and press the Crouch (B) button to hug the column. Slide down to the ground.

Go to the side beneath the entrance and break the vase to find the next Treasure (21/28). A giant spider appears from nowhere, so kill it. Go to the other side of the pit to find another vase with a Treasure (22/28) hidden in it. Again, once you get the prize, a giant spider appears from nowhere, so take care of it.