Null Void Chamber

From Ben10versepedia

In the future it is the chamber that the Null Void Projector is stored. Before the events of Ben 10,000 it was stored 61 stories beneath the main floor of Ben and Gwen's Headquarters, and any villains who were captured were taken and put into the Null Void. But during Ken 10 it was revealed that it was moved into a subspace within The Rust Bucket.