Roman monuments converted into churches

Jupiter Temple

Pantheon

Galerius Tomb (Rotunda)

Aula Palatina

The Temple Was Remade Into A Church Around 500 Ce. (Ab Ev)

Santa Maria Della Minerva: "The Roman Temple, Traditionally Dedicated To Minerva, Or Possibly To Castor And Pollux, Is Relatively Well Preserved. It Was First Converted Into A Church And Then, In 1212, Into A Prison. From 1456 The Building Was Again Used As A Church, Dedicated To Santa Maria Della Minerva In 1539." (Ab Ev)
See En.Wikipedia.Org

"From The 17th Century, The Maison Carrée Served As A Church For The Augustinian Convent Until The French Revolution, When It Became A National Property." (Ab Ev)