3. Loretto Chapel Staircase (USA)
The Loretto Chapel is a chapel in Santa Fe, New Mexico, known for its unusual spiral staircase that is an exceptional work of carpentry. The construction and builder of the staircase are considered a miracle by the Sisters of Loretto and many who visit it, because it had no central support (a support was added later). The resulting staircase is an impressive work of carpentry. It ascends twenty feet, making two complete revolutions up to the choir loft without the use of nails or apparent center support. It has been surmised that the central spiral of the staircase is narrow enough to serve as a central beam. Nonetheless there was no attachment unto any wall or pole in the original stairway. Instead of metal nails,the staircase was constructed using dowels or wooden pegs. The wood for the staircase cannot be found anywhere in the region. The stairs had 33 steps, the age of Jesus when he died. The mystery had never been satisfactorily solved as to who the carpenter was or where he got his lumber, since there were no reports of anyone seeing lumber delivered or even seeing the man come and go whilethe construction was being done. Since he left before the Mother Superior could pay him, the Sisters of Loretto offered a reward for the identity of the man, but it was never claimed.
Note: some historians claime that most of this story is a myth. (Thanks, drxwes)