Cathedral Basilica in St. Louis.
(Also known as the New Cathedral)
41.5 million pieces of colored glass,
over 7000 different colors.
Started in the early 1900s,
completed in 1914.
The side chapels were designed and
installed by Tiffany & Company.
While the main cathedral was designed
and painstakingly cemented in place
by Paul and Arno Heuduck,
who spent their entire working lives
completing this masterpiece.
(The final photo is a close up
of their mosaic work.)
Definitely worth a visit.