Just after the fourth pylon is an obelisk raised by Queen Hapshetsut. It once had a twin, but it fell over.

If you look very carefully, you'll note that the top of the obelisk is a slightly different color than the bottom. This is because the bottom was walled up by Tuthmosis III a while after he came to power.

Queen Hapshetsut took control of Egypt instead of handing it to him, and kept him under house arrest during her reign. After she died, he came to power and spent a great deal of his time defacing or covering up anything she'd ever done. This obelisk was no exception.