The St. Louis Cathedral basilica was inspired by Hagia Sophia. The interior is ablaze with mosaics, and richly decorated, so that even though it is not a replica, it is intended to evoke a similar awe and majesty. More than 41,000,000 pieces of glass tesserae illustrate numerous religious stories. This makes it the largest mosaic collection in the world. Check out this site or this for more information, and the photographs below.
Note the "stripes" / horizontal lines, the pendentives, and brilliant mosaics which are typical of the Byzantine style.
