That's especially true because their design seems upside down. While they're 18 feet in diameter at the ceiling, they are just nine inches across at the floor. How something like that could hold 60 tons is a small bit of Frank Lloyd Wright magic. But that's exactly what they do.
This sentence irked me. How something that is 9" across can hold 60 tons is not magic, it is pretty straight forward engineering. Doing the code required design calculation for this column gives a nominal capacity for this column of around 100 tons. Buckling of this column would most likely not be a an issue due to the generous taper of the column if one were to actually do the math.
This is not magic. This is basic engineering.