Sleighs slide "up" the optical illusion slides created at the Hakkaisanroku Ski Area in Minami-Uonuma, Niigata Prefecture. (Kazuhiro Itami)

MINAMI-UONUMA, Niigata Prefecture--Sleigh riders took to the slopes that appeared to defy the laws of physics at a ski resort here on March 4, apparently sliding upward.

The mind-boggling display was a trick of the mind, however. The slopes did adhere to gravity, and looked quite normal when seen from ground level.

The 10-by-10 meters squared structure’s central part is raised about 1 meter from the ground, and gentle slopes extend in four directions from it. One of the slopes is outlined to look like a flight of stairs.

When it is viewed from a particular vantage point on a 7.3-meter hill, 18 meters away, it creates an optical illusion by making the central part seem sunken. Seen from the right position, sliding sleighs or rolling balls appear as if they are moving up the slopes.

The fun feature is the brainchild of Kokichi Sugihara, a specially appointed professor of applied mathematics and physics at Meiji University, who is a master of optical illusion.

Sugihara explained that it works because “the brain conjures up depth.”

The snow slides feature is part of an exhibition on optical illusions at Ikeda Art Museum in the city, near the ski field, that is being held through March 27. The structure was built for a one-day event, but it will be kept in use for the skiers for the time being.