St. Peter’s Basilica, Rome, Italy | by voldy92
Saint Peter and Paul Cathedral
St. Petersburg, Russia | by ahvallj
St. Petersburg, Russia | by Gabriel Ortiz
Art nouveau stained glass designed by Alphonse Mucha inside St. Vitus Cathedral in Prague, Czech Republic
submitted by: thescepteredisle, thanks!
Dubrovnik, Croatia | by Dennis Jarvis
Siena Cathedral - Siena, Tuscany, Italy | by Phlipp Klinger
St. Petersburg Russia | By Tiberio Frascari
The Three Graces of Siena - Tuscany, Italy | by Philipp Klinger

allthingseurope: Canterbury cathedral, UK (by Karel de Beer)
enchantedengland: aenglaland (not aengland) where I found this, is a blog “purely dedicated to the glory of English history as well as old English architecture and art” and it is truly fabulous.
God’s lantern - Metz Cathedral, Metz, France | by mujepa
Cathédrale Saint-Sauveur d’Aix, Aix-en-Provence, Provence-Alpes-Côte d’Azur, France
submitted by: greyslate, thanks!
Cathedral in Toledo, Spain.
submitted by: havewinewilltravel, thanks!
Worcester Cathedral ♦ Worcester, England | by Doris
A Cologne Classic ♦ Cologne, Germany | by _flowtation
Moscow’s Cathedral and Towers ♦ Moscow, Russia | by b80399 
Opaque  by  andbamnan