Hirnaltaan Tower was the tallest building in the galaxy.
The Tenth Doctor took Heather McCrimmon to the tower on the day of its grand opening. When the party was attacked by Acrylamide Assassins, Heather and the Doctor followed the assassins to Vawn and Blubb. The Doctor deduced that Blubb had hired the assassins to attack the party and damage the structure of the tower. The assassins escaped, but Blubb was arrested by the Judoon. (COMIC: Night of the Burnt Toast)