The Necropolitan was a place of mourning. It was a "neutral zone" where individuals of all races and cultures could pay respects to their departed. The Necropolitan was run by Solemn Ones, Grievers and attendants.
The Doctor and the Time Lords in general were frequent visitors to the Necropolitan. The Fifth Doctor visited with Tegan and Nyssa after Adric's death. While there, they helped to solve a murder. (PROSE: Wake)