Hármashatár-hegy, Mountain summit in Budapest, Hungary.

Dreihotterberg is a 495-metre dolomite summit in the Buda Hills, on the border of Budapest's 2nd and 3rd districts. Its steep eastern slope toward the Danube drops over 400 metres within 2 km, the largest such drop in the range. The summit holds television and radio towers and a restaurant, reached only by the blue Country Blue Trail.

The mountain gained its name in the 19th century as the meeting point where three separate cities converged: Buda, Óbuda, and Pesthidegkút. This boundary marker role between settlements became central to its identity.

The name comes from the three-city border that met on the summit until 1873, when Buda, Óbuda and Pesthidegkút still shared the peak; today the line between Budapest's 2nd and 3rd districts runs across it. The mountain also keeps the memory of King Matthias's hunting park, whose Nyék hunting castle foundations and rampart remains were uncovered in the 1930s, remembered by the Vadaskerti utca and Vadaskerti-hegy names.

Access to the summit is via the blue marked trail, which passes through natural surroundings as it climbs. Wear appropriate clothing for the season and allow enough time for the walk at a comfortable pace.

The summit's bare, treeless top makes it noticeably windier than the city below, and snow can linger there up to two weeks after it has melted in Budapest. The non-public Hármashatárhegy Airport (ICAO code LHHH) lies on the mountain, with a single 1000 x 100 m runway.