Borealis

The Borealis is a ship owned by Aperture Science. It first appeared in Half Life 2: Episode 2, but it can be found in Portal 2 as an easter egg, hidden in Chapter 6,

Portal 2
In Chapter 6: The Fall, The Borealis' drydock can be found in Test Shaft 09, during the 70s section. It is hidden behind a door in one of the offices, the drydock is empty, but life preservers are seen, with the word 'Borealis' written on them.