The A-listed St Peter's Seminary in Cardross, Argyll, named as one of the world's most endangered sites by the World Monument Fund, has secured £565,000 to further develop its plans, with a future bid of £3 million expected to be granted in 2015.
The Heritage Lottery Fund (HLF) award is the biggest move yet in securing its future, which has lain derelict for almost 30 years despite its status as a masterpiece of modernism.
The seminary was designed by the leading Scottish architectural firm Gillespie, Kidd and Coia for the Archdiocese of Glasgow in 1966, but was closed in 1980, and, with the exception of a few years as a drug rehabilitation centre, has lain abandoned and vandalised ever since.
Arts charity NVA acquired the building on "conditional missives" from the Catholic Church several years ago and has modified its proposals recently.
The proposals have also been garnering international support since they were presented at the Venice Biennale in 2010. Over the next year NVA must raise a further £3.5m, while a major public campaign that will be launched early in 2014.
The works will partially restore the chapel, preserve the derelict seminary buildings as a "raw frame" and reinvigorate the surrounding 45 hectare woodland and productive gardens, gradually bringing the site back to life.
There will also be reclamation of the main pathways and repair of the historic bridges and late mediaeval castle keep. The Victorian walled garden will be brought back into public use and will become the main 'social focus'. A new pavilion building will be designed via an architectural competition and act as the hub for the public activities.
Angus Farquhar, NVA's creative director, said: "The HLF award towards the resuscitation of St Peter's represents a pivotal moment for the history of 20th Century architecture. The seminary building is held in high regard throughout the world. It has now been given the chance of a second life after 25 years of decline. The proposals will deliver an iconic cultural resource where powerful art and heritage learning will sit side by side.
"The remarkable site history spans the arrival of Irish monks 1,500 years ago, to becoming the fabled hunting ground of kings and later the transformation from grand estate to a vast religious institution. Now nearly 50 years on from the day it opened we witness the first steps in a new and radical form of regeneration."