One of Scotland's most important modern structures, it just made the '100 Most Endangered Sites' list
St. Peter's exterior
Remnants of living quarters.
Remnants of living quarters.

The great library (overhead)
Remnants of living quarters.
The great library (overhead)
St. Peter's Seminary
Remnants of living quarters.
The great library (overhead)
Strolling through the countryside of Scotland you expect to see the ruins of an ancient castle or two - the hillsides are full of them. However, tucked away in the woods outside Cardross lies an entirely different kind of relic.
The ruins of St. Peter's Seminary are seemingly not of this world. Its as though you've stumbled upon the remnants of an ancient alien civilization. In appearance the word "brutal" is an understatement. Daunting, ghastly, decimated are all appropriate descriptors.
Alien as they may appear, St. Peter's function was quite quotidian, and as far as ruins are concerned, they are not very old.
Designed in 1958 by Gillespie, Kidd, and Coia, it's an A-listed building that sits on several preservation lists for being an excellent example of Scottish modern design. So, what brought this spiritual hall of learning to such a sorry state?
By the time St. Peter's Seminary was completed in 1966 its function was obsolete. The Roman Catholic church had recently decided that priests should train in communities rather than the isolation of remote seminary colleges. To compound problems, church attendance in Scotland was declining, as well as the number of young men wishing to enter the priesthood. This left St. Peter's, a school designed to house and train a hundred would-be priests, with a residency of only twenty some students by the late seventies. In 1980 St. Peter's permanently closed it's doors.
Since then, neglect, the elements, a sizable fire, and nearly daily vandalism have taken their toll, reducing the seminary to a hulking skeleton.
From Atlas Obscura, Thanks!
Gillespie, Kidd & Coia: Architecture1956-1987