The Manti Utah Temple has some of the most unique spiral staircases in the world. In the two west corner towers there are freestanding spiral staircases without central supports. If you attend this temple, ask a worker to see the staircases and they will take you to see them. They have incredible craftsmanship. When they restored the temple for the centennial they found something like 2 creaks in the one staircase and none in the other, despite being heavily used by temple workers and used by patrons to access several sealing rooms in the towers. The seams between pieces of wood on the railings are also extremely difficult to find.
I said that these were some of the most unique staircases in the world. That is because there are only a few free standing spiral staircases that lack central supports in the world. I believe there are only eight in the U.S. with two being in the Supreme Court Building (those are elliptical). So the Manti Temple spiral staircases are really special.
One of the staircases goes up clockwise and the other counterclockwise. They really are an impressive sight and a great asset of the Manti Temple.
More on Temple Staircases by Scott: THE TRUMPET STONE
More photos of the Manti Temple: Manti Temple