Placed as a reminder of art that was stolen, destroyed or went missing under Nazi rule in 1937, the piles of fake horse manure which were installated in Berlin this summer can be seen at the New National Gallery.

Made up of artificial dung, Martin Gostner's work, The Oriel of the Blue Horses, features four piles of fake blue manure. Each pile corresponds to one of the horses in Franz Marc's seminal work The Tower of Blue Horses.

The expressionist masterpiece was branded "un-German" and "degenerate" by the Nazis and to this day it is not known whether the work was destroyed or hidden away, and it has never been found. The aim of the piece, according to Berlin's New National Gallery, is to make it seem as though the horses are alive and trotting around the museum.

"What would happen if the painting still lived, if there were a sign of it, and the horses were to come by here?" said Dieter Scholz, the gallery's curator. Marc's painting was bought in 1919 by Ludwig Justi, the director of the New National Gallery, and was part of the museum's collection until its confiscation. Like many works that went missing during the period, it is not known if The Tower of Blue Horses still exists or has been destroyed.

Prior to 1949 there were various sightings in Germany and there were unconfirmed reports it had been stored in a Swiss bank safe.

The New National Gallery’s permanent collection includes work from many artists, including Max Beckmann, Otto Dix, and Ernst Ludwig Kirchner, who were also labeled "degenerate" by the Nazis.