Cyber Portal
The Cyber Portal in the "Back to the Sewer" season of the 2003 series was a transport device that allowed the Turtles to enter the world of cyberspace and return safely to the real world. Donatello Splinterson constructed it in order to reclaim Splinter's scattered data bits.
When Donatello was under his control, the Cyber Shredder successfully gained the information to create his own cyber portal.