In the city of Santa Fé, in New Mexico, USA a mystery of over 130 years old exist. It attracts around 250 thousand visitors every year.
Point of attention : Loretto Chapel
The construction of the chapel was commisoned towards the end 19th century by Jean-Baptiste Lamy, the Bishop of the Santa Fe Archdiocese. The convent chapel was to be named Our Lady of Light Chapel, which would be in the care of the Sisters of Loretto. The chapel was designed by French architect Antoine Mouly in the Gothic Revival style, complete with spires, buttresses, and stained glass windows imported from France. Although it was built on a much smaller scale, the chapel bears an obvious resemblance to the Sainte-Chapelle in Paris.
No!. This is not the mystery..
What makes this chapel different from all others is that the subject of the supposed miracle that took place in it is a Staircase. When the chappel was ready, the nuns found that there was no staircase built to take them to the choir loft. The architect died suddenly and due to the chapel's small size, building a standard staircase would have been too large for the chapel..
The reputed story continues as follows..
The nuns prayed for St. Joseph's intercession for nine straight days. On the day after their novena ended a shabby looking stranger appeared at their door. He told the nuns he would build them a staircase but that he needed total privacy and locked himself in the chapel for three months. He used a small number of primitive tools including a square, a saw and some warm water and constructed a spiral staircase entirely of non-native wood. The identity of the carpenter is not known for as soon as the staircase was finally finished he was gone. Many witnesses, upon seeing the staircase, feel it was a miraculous occurrence.
The staircase thus built, 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, although 10 years later a railing was added and the outer spiral was fastened to an adjacent pillar. 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 while the 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..
For Further Reading.. 
Title:“Loretto: The Sisters and Their Santa Fe Chapel (2002: Museum of New Mexico Press)
Author: Mary Jean Straw Cook
$22.50
Buy it from Amazon here
