The as yet unfinished building, a little over 20 km outside of Madrid, has been painstakingly built piece by piece over 50 years by 86-year-old farmer Justo Gallego Martinez.
He had no prior knowledge of architecture and no experience in the construction industry, but instead has spent five decades collecting junk and discarded building material in order to build the 35-metre tall structure.
After working as a farmer and bullfighter, deeply religious Senor Martinez – or Don Justo as he is known – spent eight years at a Trappist monastery.
But he was forced to leave when he was struck down with tuberculosis in 1961.
During his illness, he vowed that if he survived it he would build a chapel and name it after the Virgin Mary to whom he prayed while he was sick.
True to his vow, Don Justo began building what he describes as his act of faith in 1963 and despite his lack of skills or building materials, is still working on the project today.
Despite the scepticism of many friends and locals, Don Justo has remarkably managed to build the place of worship without using so much as a crane.
The vast columns of the structure are made from empty oil drums, while the covering on one of the domes is made from discarded food tubes.