Cathedral Basilica of Saint Louis

25 Most Popular Tourist Attractions

Built after the turn of the 20th century and something of a curiosity, this cathedral combines a Romanesque exterior with a brilliant Byzantine interior and boasts the largest collection of mosaics in the world -- 42 million pieces of glass used in 83,000 square feet of mosaic art, created by 20 artists over a span of 75 years. Plan at least 15 minutes for this must-see.

Though the Cathedral Basilica's Romanesque exterior is undoubtedly impressive, the interior of the cathedral is what is truly inspiring. The seat of the Catholic archdiocese in St. Louis, this massive complex contains a mosaic collection that is said to be the world's largest. Over the course of 76 years, 41.5 million pieces of glass tesserae were affixed to the walls and ceiling to illustrate...