Starting the second chapter, The Cold Boot, it is the first chamber GLaDOS sends Chell through after her.

Chell will witness the drastic changes of these chambers from being overgrown and ruined, to a more clean and perfected state. Since her awakening, GLaDOS has been fixing not only the chambers related to the test course, but the entire Enrichment Center itself. This testing course was used after GLaDOS had been reactivated by accident, courtesy of Wheatley. The final chamber for this course would have been Test Chamber 22, which is a death trap for Chell. Its start, the very last test chamber from the original testing track in Portal, is connected to the Incinerator Room. GLaDOS' Testing Track (Portal 2) is the newly built testing course featured in Portal 2, consisting of 22 test chambers.