St. Marks Basilica is truly great, it is a project which the Republic of Venice worked on for many centuries. Perhaps the biggest advancement in its grandeur was after the Venetians stripped as many things as they could from Constantinople to put on and in the church. The visual below shows the kind of upgrade which resulted from it, though much of it was also added later in the renaissance to be fair and accurate.
One can look on the outside of the church and start spotting Byzantine features rather easily. There are marble panels, relief sculptures, colorful marble columns, and column capitals all coming from Constantinople. There are mixed in with the stolen columns, some Venetian imitation columns as well. Porphyry however was not available at the time, and thus it is all spolia.
The effort it took to transport so many columns across the sea to Venice from Constantinople must have been considerable, but clearly it was worth it to the Venetians. These columns from antiquity were expensive to make, and in some cases medieval artisans in Venice may not have had access to some stones like porphyry at all – other than spolia.
The exterior of St. Mark’s Basilica really shows itself in some areas as the result of a crusader pick & pull at Constantinople when one looks closely. It is a random assortment of looted marble panels, relief sculptures, and columns. It’s not always very gracefully put together, the product of a thorough Venetian scavenger hunt in Constantinople. It is undoubtedly interesting to look at, while showing just how systematic the looting was.
SOURCES:
Columns and Capitals http://www.basilicasanmarco.it/basilica/scultura/colonne-e-capitelli/?lang=en#:~:text=There%20are%20more%20than%20500,the%206th%20and%2011th%20centuries.