Gallego Martínez began construction on a farmland owned by his family on October 12, 1961, after he could not complete his novitiate at the Cistercian monastery Monastery of Santa María de Huerta, due to his tuberculosis.[1]

After his condition improved, he promised to thank God, and the Virgin Mary, by constructing a church building. And, over the course of many years, using family assets, selling his land, as well as private donations, he was able to work on the building.

Gallego has dedicated more than 50 years to construct the building until his death. With the exception of some help from others, the near entirety of the "cathedral" has been constructed purely by Gallego, who had no qualifications in any form; his studies had been interrupted during the Spanish Civil War. Gallego constructed the building without any plan, public funding or official building permits.[2]

The inhabitants of Mejorada del Campo know the project as "cathedral of Justo", and is what the town, which is 20 kilometers from Madrid, is known for. The ground has been used for religious ceremony, but it has not been consecrated.[2] The project has received various external interest, the Museum of Modern art in New York presented photos of the architectural in a temporary exhibition in 2003-2005.[3]

Gallego died on 28 November 2021. The building was donated to the Catholic organisation Mensajeros de la Paz (Messengers of Peace) just before his death to allow the construction to be completed.[4][5]