The Loretto Chapel in downtown Santa Fe is well known for the "miraculous" staircase within.
The chapel.
"The staircase referred to as miraculous, inexplicable, and marvelous confounds architects, engineers and master craftsmen. It makes over two complete 360-degree turns, stands 20’ tall and has no center support. It rests solely on its base and against the choir loft. The risers of the 33 steps are all of the same height. Made of an apparently extinct wood species, it was constructed with only square wooden pegs without glue or nails." (from the Chapel's website link above). It is an impressive sight.Seems like it should collapse upon itself under its own weight.