Höllensteinhaus, A shelter of the Austrian Friends of Nature on the summit of the 645 m high Höllenstein in the Vienna Woods.

The Höllensteinhaus is a mountain hut and observation tower on the Höllenstein at 645 meters in the Vienna Woods near Kaltenleutgeben. The simple building with large windows stands among trees and offers seating both inside and outside, with a kitchen that serves food and drinks to visitors.

The Mödlinger "Verein der Naturfreunde", founded in 1877, built the Julienturm around 1880 and added a small annex on its east side in the early 20th century. After World War I the tower and annex passed to the "Touristenverein Die Naturfreunde", founded in 1895, which demolished the annex and erected the Höllensteinhaus in 1924. The hut burned twice in June 2007, partly on the 23rd and down to the foundations in the night to the 26th; after repairs it reopened on 20 September 2009.

The hut is run by Naturfreunde Österreich, the nature friends association founded in 1895 that acquired the tower and its annex after World War I. The Julienturm beside it is named after Julie Regenhart von Zápory, whose husband Franz Ritter Regenhart von Zápory paid about half the tower's construction costs.

The hut sits at 645 m on the Höllenstein summit, reached on foot only; the shortest approach starts at Wassergspreng with about 285 m of ascent and takes roughly one hour. From Kaltenleutgeben the climb is about 280 m and 1 1/4 hours, from Gießhübl about 230 m and 1 1/2 hours, and from Rodaun, the terminus of tram line 60, 2 1/4 hours. The hut was rebuilt after fires in June 2007 and reopened on 20 September 2009.

The Julienturm was built around 1880 by the Mödlinger Verein der Naturfreunde and named after Julie Regenhart von Zápory, whose husband Franz Ritter Regenhart von Zápory paid about half the construction costs. In 1896 the brick tower was rebuilt and raised by roughly four metres.