Borealis

The Borealis is a ship used to gather information from and to Aperture Science.

Purpose in Half-Life 2: Episode 3
The ship will be the stage area for the game, but Aperture Science employees might not notice Gordon Freeman and Alyx Vance entering the ship, trying to find Dr. Judith Mossman who had information about the Borealis. Sometime in the game, Freeman might be given a tutorial on how to use the Portal Device from Alyx.

Appearance in HL2: Episode 2
The Borealis makes a brief appearance in the prequel. Dr. Issac Kleiner and Eli Vance debated on whether the Borealis would prove useful or ruin their triumph against the Combine forces. Dr. Kleiner gave Alyx the coordinates for the ship and in the sequel, Freeman and Alyx will find out if the Portal Device will prove to be a useful tool or be a threat to them.

Appearance in Portal 2
The Borealis may be found in the abandoned underground area of Aperture Science, in a hidden area that is found in the room that is above the one where you find potatOS(GlaDOS in the potato). Within that room is a door that is slightly blocked off by various office equipement, but once approached, will open and may be accessed by jumping onto the right side and crouching through the open space through the door. In the room behind the door, is doors with interactive panels next to them explaining the purpose of each room behind the door. One door, however, is open and in that room can be found, what appears to be two large ships. On the ground lies many life-buoys with the words Borealis on them.