An Obelisk is a recurring symbol within the Shin Megami Tensei games, commonly of unknown origin.
Shin Megami Tensei III: Nocturne
The only Obelisk seen in the Vortex World is located near the Manikin city of Asakusa, and later becomes the Tower of Kagutsuchi.
Shin Megami Tensei IMAGINE
The three Obelisks appeared after the construction of Shinjuku Babel, and vastly altered the appearance of the regions they appeared in. They are located in Nakano, Ichigaya, and Shibuya.
The Obelisk in Shibuya, which created crystals of quartz
The Obelisk in Nakano, which created a forest
The Obelisk in Ichigaya, which created a lava-strewn wasteland