I am not a Christian, or religious at all, but there are some wonderful Christian churches. Most of southern Europe is Roman Catholic and Catholics are the best at producing over-the-top decoration.
After the Reformation in the 1530s, most of northern Europe made Catholicism illegal. Monasteries were destroyed, church property confiscated, most Catholics fled, were imprisoned or executed and almost all churches became Protestant. Lutherans especially disdained the icons and decoration of Catholic churches, removed everything and painted the insides of the churches white.
I have travelled to about 192 countries and have not seen all Christian churches, but I’ve seen a lot. This is my list of my favourites. Most are free to enter. The first three could all be tied for first place.
1. PALATINE CHAPEL, Royal Palace, Palermo Sicily
2. CHURCH of the SAVIOR ON SPILLED BLOOD, St Petersburg Russia
3. MONREALE CATHEDRAL, Monreale Sicily
4. WESTMINSTER ABBEY, London England
5. TEMPLO de SAN JUAN, San Juan Chamula, Mexico
6. SAGRADA FAMILIA, Barcelona Spain
7. BURGOS CATHEDRAL, Burgos Spain
7B. TEMPPELIAUKIO CHURCH (ROCK CHURCH), Helsinki, Finland
8. SANTIAGO de COMPOSTELA CATHEDRAL, Santiago, Spain
10. HABO KIRKE, Jonkoping Sweden
11. THE CHURCH of OUR LADY of GOOD HOPE, Fort Good Hope, North West Territories Canada
14. ABBEY CHURCH OF SANTE FOY, Conques, France
15. TEMPLO del CARMEN, San Luis Potosi Mexico
16. BASILICA de NOTRE-DAME de la PAIX (Basilica of our Lady of Peace) Yamoussoukro, Cote d’Ivoire
17. ORIATORIO di SANTA CITA, Palermo Sicily
18. MONASTERE de CHEVETOGNE, Ardennes, East Wallonia Belgium
19. NORWICH CATHEDRAL, Norwich England
20. AACHEN CATHEDRAL, Aachen Germany
21. ROSSLYN CHAPEL, Edinburgh Scotland
22, PETÄJÄVESI OLD CHURCH, Petäjävesi, Finland
23. STAVE CHURCHES, Norway