Iconian Gateway

An Iconian gateway, or trans-dimensional gateway, is a technology developed by the ancient Iconians 200,000 years ago in Star Trek: essentially a sophisticated transporter whose principles remained well beyond Federation science. A gateway appears as a door, suspended in space or surrounded by a frame, that a traveller steps through to arrive instantly over distances of at least 70,000 light years; the network let the Iconians control their empire without starships. Only two gateways were known to survive: one on Iconia, destroyed by the Enterprise-D away team in 2365, and one on Vandros IV in the Gamma Quadrant, retaken and destroyed by a joint Starfleet and Jem'Hadar team in 2372.