In the game "Half-Life," the Borealis is a research vessel constructed by Aperture Science in its bid to win funding that was originally going to Black Mesa. During construction, Aperture Science neglected some common safety rules, and the ship simply disappeared.
It is rumored that the Borealis contained a very powerful secret related to portals and teleportation on a scale much larger than a hand-held device. During "Half-Life," the Combine showed a particular interest in finding out its secrets. It is theorized that by using the teleportation power of the Borealis, the Combine could form a large portal back to the Combine Overworld and subsequently flood planet Earth with its armies. The original dry dock is a hidden secret in the game Portal 2.