Sophisticated dimensional transport system, in use by the ancient Iconians 200,000 years ago, that allowed instantaneous movement across interstellar distances without the use of starships.

The first known discovery of an Iconian gateway in modern times was in 2365 by the crew of the Enterprise-D on the planet Iconia.

The Enterprise-D crew destroyed the gateway rather than allow it to fall into Romulan hands. "Contagion [TNG]"

A second gateway was discovered by Dominion scientists in 2372 on planet Vandros IV in the Gamma Quadrant.

The gateway was housed in an ancient stone ziggurat whose internal structure was constructed of neutronium, making it impervious to external attack, even by quantum torpedoes.

Rebel Jem'Hadar soldiers attempted to seize the gateway, but were prevented from doing so by an unusual joint mission of Jem'Hadar and Federation forces that destroyed the gateway mechanism and its surrounding building.