Iconian gateways are portals built by the ancient Iconians that can send a person instantly across vast distances, discovered by Starfleet in 2365.
The Iconians were an advanced civilization believed to have been destroyed some two hundred thousand years ago. In 2365 the USS Yamato was destroyed after its systems were corrupted by Iconian software sent from a probe launched on Iconia, and the Enterprise-D was nearly lost to the same program. Picard found a working gateway on Iconia and destroyed it to keep it from the Romulans.
Another gateway was found on Vandros IV in 2372, where Jem'Hadar renegades hoped to use it to conquer. Sisko's crew and a team of loyal Jem'Hadar under Weyoun joined forces to destroy it.