I.M. Pei's staircase at the Louvre

The Louvre in Paris is considered to be one of the finest and most complete collections of fine art anywhere in the world. With the city being an international cultural capital for hundreds of years, it's only fitting that one of Paris's landmark institutions is also one of the most architecturally controversial structures in the world.

In 1984, French President François Mitterrand commissioned the expansion of the Louvre Palace in the heart of the city, calling upon renowned architect I.M. Pei to oversee the design. Pei and his firm are known for their highly modernist structures that have been called upon for commercial, residential and cultural use the world over.

Completed in 1989, the centerpiece of the renovation was a massive 71-foot-tall glass pyramid at the center of the palace's main courtyard. Beneath the structure is a massive subterranean foyer that functions today as one of the main entrances to the museum's galleries. In contrast to the Beaux-Arts style of the original palace, this structure features no masonry but simply a steel frame and high-strength glass panes. 

Visitors descend from the outside into the underground courtyard via a wide spiral staircase that curves downward in a single sweeping coil. The stairs themselves feature off-white stone treads on top of a smooth metallic slide that unwinds down to the second level of the building. The balustrades feature stainless glass railing without any balusters or newel posts. Instead, a clear pane of glass works as the main handrail support .

This staircase is lauded by architectural critics for its seemingly simplistic approach yet visually rich and aesthetically complex look. When viewing the structure from below, it contrasts beautifully with the rigidity of the glass pyramid.