Seattle Space Needle is a monumental tower located in the USA. It also happens to be an abandoned Plumber base.
It appeared in Ben 10 vs. the Negative 10: Part 1 and is the location of the second key to the force field protecting the Sub Energy in Mount Rushmore. The location was attacked by the majority of the Negative 10, and it is the location of the first battle of the Tennysons against the Negative 10. The Key is stolen by Rojo in the middle of the battle.