Mysterious flights of stairs float in mid-air or form elevated outdoor walkways in this series of installations by artists Lang/Baumann (+ slideshow).

Among the installations in Lang/Baumann's Beautiful Steps project is a curved white staircase that hangs in the hall of Trautenfels Castle in Austria, contrasting with the richly coloured frescoes on the ceiling.

They also installed an open walkway that loops around the outside of the castle and is accessed by steps under the windows.

An aluminium staircase connected by false doors was constructed on the exterior of a building in Biel/Bienne, Switzerland. The building appears taller than it is because the grid of windows doesn't match the ceiling heights, so the artists made their work to a slightly smaller scale than a normal door and stair to accentuate the illusion.

Another staircase with lopsided steps was installed between the floor and ceiling of a Parisian art gallery, Galerie Loevenbruck, and can be adjusted to different heights by adding or subtracting steps.

They also suspended a wonky staircase inside the Fundación PROA museum in Buenos Aires and planted an arched staircase on a lawn in Lausanne.

Swiss-born Sabina Lang and San Franciscan Daniel Baumann have worked together since 1990 and are based in Burgdorf, Switzerland.

Other unusual steps we've featured include a concept for a staircase based on a whale's backbone and a suspended staircase that leads down to steps built into a kitchen counter – see all staircases.

See all installations »

Here's some more information from the artists:

Beautiful Steps #2 - 2009 Biel-Bienne CH, Utopics. 11th Swiaa Sculpture Exhibition

Technique: steel zincked, anodised aluminium

Dimensions: 177 x 523 x 458 cm

Curator: Simon Lamunière

The congress building in Biel-Bienne plays a trick on perception: because the diminutive grid of its large glass front does not match the ceiling height of the floors, the building appears taller than it ismore like a skyscraper than its actual 50 meters (164 foot) of height. The building also features an unusual concrete structure that encloses one half of the volume like an oversize frame, leaving a gap on one side between itself and the building. On this pillar, almost three-quarters of the way up, an aluminum stair was attached, leading from one fake door to another around one corner of the structure. In keeping with the optical illusion of the building, the work was built to a slightly smaller scale than a normal door and stair. The slender sculpture plays with an imaginary functionality.

Beautiful Steps #3 (Trautenfels) - 2010 Schloss Trautenfels A, Regionale. Fabricators of the World. Scenarios of Self-will

Technique: wood, paint

Dimensions: 11.5 x 5 x 4.3 m

Curator: Adam Budak, Peter Pakesch

A white, curved stair, slightly askew and suspended in midair in a baroque castle hall, was held aloft by a few slender, almost invisible cables. The lean shape and the white surface of the sculpture formed a striking contrast to the lush frescoes on the ceiling.

Beautiful Steps #5 - 2010 Schloss Trautenfels A, Regionale. Fabricators of the World. Scenarios of Self-will

Technique: laminated wood, paint

Dimensions: width of the step 70 cm, height 110 cm, diameter 8 m

Curator: Adam Budak, Peter Pakesch

Two curved stairs ascended to two windows at right angles. Outside each window a curved walkway projected into the air and disappeared in a loop around the facade of the building. Viewed from the outside, the walkway could be seen to connect the two windows like a fragile band around the castle's corner tower. Interior and exterior elements of the scultpture formed a complete circle.

Beautiful Steps #8 - 2011 Galerie Loevenbruck, Paris F

Technique: wood, lacquer

Dimensions: height 310 cm, diameter 250 cm

Courtesy: Galerie Loevenbruck Paris

A winding stair, slightly askew, was mounted between floor and ceiling of the gallery. Somewhat smaller in scale than an actual stair, the functional aspect of the sculpture was further diminished. This modular piece can be adjusted to different ceiling heights by adding or subtracting steps.

Beautiful Steps #9 - 2012 Vaudoise, Lausanne, CH

Technique: stainless steel, lacquer

Dimensions: 2.5 x 3.7 x 3.5 m

A fragment of an impossibly twisted circular stair rises from the ground and leads nowhere. While invisibly anchored in the ground, the sculpture inexplicably stands upright on its own. The first step is horizontal and parallel to the ground, but with each successive step the stair torques away from its original axis by 5 degrees until it projects into space at a steep angle. Adding to the drama, a continuous reduction in riser height emphasizes the foreshortening of the sculpture towards the top.