Tomb of Menkaure
Note that you'll pass through here during the What's Yours is Mine Side Quest.
Enter this tomb through a tunnel very low on the north side of the pyramid.
Go inside, then down the ramp to find the main treasure room.
Loot it thoroughly, then follow the passage down for another treasure room.
There is some silica here, and one of those snake-hiding urns.
Retrace your steps back outside, but just before exiting the complex, take the small tunnel just above the exit instead.
Light an arrow to dispose of the wooden ceiling at the end of the tunnel.
Inside you'll find even more loot, and the stone tablet for this tomb.
Reading the tablet completes the location, and grants an ability point.