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The
Loretto staircase – built within the Loretto Chapel in New Mexico, USA – is by far the most remarkable staircase ever built. It features a double-helical spiral structure that spans 20 feet in altitude, and remains intact without the use of a central pole. The staircase is built mostly out of wood and is held together by wooden pegs and glue rather than nails or other hardware.
The staircase is venerated by Catholics as being miraculous, not due to its marvel, but based on the events that have been passed down by the Sisters of chapel ever since it was built in the late 1800s. Before the construction of the Chapel could be completed, the architect responsible for the building's design had suddenly died, leaving the nuns without access to the choir loft. Multiple builders were consulted, but were not able to find a workable solution due to the confined quarters. In response, the nuns prayed for nine straight days to St. Joseph, the patron saint of carpenters. On the last day of their prayers, a mysterious stranger appeared and offered to build the staircase. He worked alone using only a few simple hand tools and disappeared afterwards without collecting his pay or the Sisters learning his identity. To add to this mystery, the exact species of wood used to build the staircase is unknown, and DNA extraction from the wood show that it is non-native to New Mexico.