In Stargate SG-1
"Supergate" A gigantic Stargate designed to allow the passage of starships. The Supergate is made up of 90 smaller pieces that are moved through a regular Stargate. Once assembled, a nearby planet is collapsed into a quantum singularity, using a special force field, in order to provide the massive power needed to open a wormhole to the Ori galaxy. Samantha Carter theorizes that the singularity allows a connection to be maintained indefinitely. The first Ori attempt to create a Supergate in the Milky Way fails when Vala Mal Doran inserts her Tel'tak into the incomplete ring and prevents the segments from completely connecting. The shockwave from the forming singularity then blasts the gate to oblivion. A second Supergate is later built successfully and allows a fleet of Ori motherships into the Milky Way. The SGC eventually blocks the Supergate to the Ori by opening a connection from a Pegasus gate powered by a "natural" black hole.
Read more about this topic: Quantum Singularity