The Dehnepark is a big, beautiful forest in Viennas district of Penzing with lakes in it. It is part of the Wienerwald (Vienna Woods), a wide forested highland scenery in the states of Lower Austria and Vienna.
This trail, the Stadtwanderweg 4, is leading through the Park.
https://de.wikipedia.org/wiki/Dehnepark (german)
https://en.wikipedia.org/wiki/Vienna_Woods