The Observatory and the Rainbow Bridge.
The Bifrost is an interstellar portal which allows travel to any of the Nine Realms. It is located in Asgard, and is guarded and controlled by Heimdall.
The Bifrost Bridge is controlled from Heimdall's Observatory that is connected to Asgard via the Rainbow Bridge. Heimdall's sword or Gungnir can activate the portal which could destroy planets with its energy if left opened.