St Peter’s Seminary near Cardross, Scotland, was used as a college only from 1966 to 1980. It was repurposed as a drug rehab clinic, which closed in 1987. Since then, it's been left empty and abandoned.
Designed by Gillespie, Kidd and Coia, St Peter’s Seminary is an important example of modernist and brutalist architecture. Although buildings like this are often negatively associated with urban decay, the seminary’s geometric, functional concrete and polished wood design was probably intended to reflect the modernisation of the Catholic Church during the 1960s.
See plenty of pictures of the facility at Urban Ghosts. Link
(Image credit: Wikipedia user Mad4brutalism)