The exterior of the Cathedral of the Immaculate Conception follows the Doric Order, in an interesting late, or as I might call it, terminal Beaux-Arts interpretation of the Greek Revival designed Joseph William McCarthy.
Of course, it is architecture adapted for the modern world, as Greek temples did not have windows, whether on the side or in the clerestory.
Compare the pediment to the Archaic Greek temples at Paestum or the Old Cathedral in St. Louis. More extensive and scientific analysis of ancient Greek architecture had occurred by the early Twentieth Century, so we see more exacting detail
As is typical of the Doric, there is no foot on the column base, The Tuscan order, which often replaces the Doric in American, does have a base.
Interestingly, in the metopes, the alternating spaces in the entablature between the triglyphs, are repeating monograms of a cross and an M for Mary.
The doorways are also quite elaborate, as can be seen below.
Remember, in archaic Latin, U and V were the same letter, so that is why you often see that on buildings well into Twentieth Century America.
There are also some very nice grates over the window.
The tower over the central portal is also a nice touch, though it is always a bit interesting since the Greeks did not have towers on their temples.
But here the architect designs the tower in a classic sense of using the architectural orders, with the heavier Ionic order on the second story above the clockfaces, and then the lighter and airier Corinthian order above. You can see this on the Colosseum in Rome.
I am not sure, but I can’t help but wonder if there may have been a different roof planned for the termination of the tower.
Still it’s an interesting solution for a Greek Revival church.