Answer: Tartarus
Explanation: When the Titans waged open war on the Olympian gods and lost they were sent to dwell in the Tartarus. In Greek mythology, Tartarus is a deep abyss in the Underworld which serves as a prison for the Titans. Afterward, it also served as a place of torments for the wicked. Other gods could be sent to the Tartarus also, as it happened to Apollo.