Question

What purpose do the obelisk of senusret and other obelisk serve

Answer 1

Obelisks were found mostly at the entrances to temples, but also next to tombs and often in pairs. They gave the entrance a "magical" protection. The obelisk of Senusret is today placed on a Roundabout in a city of El Fayoum.

Answer 2

Senusret I made several expeditions to the Sinai and Wadi Hammamat and he built there numerous shrines and temples. He erected 2 red granite obelisks to celebrate his Year 30 Heb Sed Jubilee. One of the obelisks is the oldest standing obelisk in Egypt. The obelisks primarily used to commemorate a pharaoh.