According to Dr. William R. Cook, Professor of Religious History at SUNY Geneseo, these are the world's greatest churches.
My favorite is Hagia Sophia.
The Church of the Holy Sepulchre
Hagia Sophia
The Cave Churches of Cappadocia
The Rock-Hewn Churches of Ethiopia
The Mosque-Cathedral of Córdoba
The Stave Churches of Norway
The Pilgrimage Church of Sainte-Foy
The Cathedral of Monreale
Chartres Cathedral
Winchester Cathedral
The Cathedral of Siena
St. Peter’s Basilica
The Wieskirche in Bavaria
La Compañía and Las Lajas Sanctuary
Guadalupe and the Cathedral of Mexico City
La Sagrada Família
Iceland’s Hallgrímskirkja
Hagia Sophia
My favorite is Hagia Sophia.
The Church of the Holy Sepulchre
Hagia Sophia
The Cave Churches of Cappadocia
The Rock-Hewn Churches of Ethiopia
The Mosque-Cathedral of Córdoba
The Stave Churches of Norway
The Pilgrimage Church of Sainte-Foy
The Cathedral of Monreale
Chartres Cathedral
Winchester Cathedral
The Cathedral of Siena
St. Peter’s Basilica
The Wieskirche in Bavaria
La Compañía and Las Lajas Sanctuary
Guadalupe and the Cathedral of Mexico City
La Sagrada Família
Iceland’s Hallgrímskirkja
Hagia Sophia
