Son's tower, or Son's cathedral housed the Son.
Ahsoka Tano was captured and poisoned her, making her turn to the dark side and attack Anakin Skywalker and Obi-Wan Kenobi. At the same time, the Son was confronted by Father and Daughter. Afterwards, the Son escaped, the Daughter sacrificed herself to save Father, and Ahsoka turned back to the light side.
The Son's tower was tall and supported a green sphere with other spheres around it. Inside the tower, there was a room with a large window and a throne for the Son. The inside was enormous, and it held a prison.