Vaskapu, Limestone cave in Pilisszentkereszt, Hungary.

Vaskapu is a limestone cave in the Pilis Mountains featuring a natural stone arch that opens above the Dera stream valley. The cave sits at roughly 570 meters elevation and is surrounded by forested terrain.

The double rock arch has been known as a climbing school since the 19th century; Ferenc Schafarzik described it in 1884 in Földtani Közlöny, and the Turisták Lapja reported on it in 1889. In 1929 the Zsigmondy Society of the Hungarian Tourist Association placed a memorial plaque here honouring Emil Zsigmondy, the country's best mountaineer, and the site has since served as a place of remembrance for Hungarian climbers.

In 1929 the Zsigmondy Society of the Hungarian Tourist Association placed a memorial plaque here for Emil Zsigmondy, regarded as the best Hungarian mountaineer. Since then Hungarian climbers have held commemorations at the rock gate. The arch is also known locally as Pilisi Vaskapu, a name recorded in Turisták Lapja in 1889.

Access to the cave starts from Pilisszentkereszt cemetery via an unmarked path marked by a green stripe trail that runs beside Dera stream. The walk is short but requires sturdy footwear for uneven forest terrain.

The double arch is 25 metres tall: the large opening measures 5–6 metres high and 5 metres wide, the small one 4 metres by 3 metres. At its base a hollow widening inward offers shelter from the weather, and the rock is Upper Triassic Dachstein limestone, probably formed under phreatic conditions.