Hallthurm, Mountain pass and heritage monument in Berchtesgaden Alps, Germany.

Hallthurm is a 693 m high mountain pass in the Berchtesgaden Alps near Bischofswiesen, where the Lattengebirge and Untersberg ranges meet. At the pass summit stand the name-giving defensive tower and remains of fortifications built around 1194 by the Berchtesgaden monastery, with walls up to 2 m thick. The B20 road, the Bad Reichenhall–Berchtesgaden railway and the brine pipeline all cross the pass.

The site was known as a guarded crossing point in the medieval period, when a tower was built there to control movement through the mountains. Over time the tower lost its defensive role but was kept as a monument.

The name Hallthurm refers to an old tower that once guarded the crossing, and that name has stayed with the place ever since. Visitors can still spot remains of this structure along the roadside as they pass through.

The pass is open throughout the year and can be reached easily by road, though winter driving in the Alps always calls for caution. Those who want to look at the monument more closely can stop along the roadside where space allows.

Hallthurm is one of the few places in the Bavarian Alps where a medieval defensive tower stands directly alongside a modern federal road. Both structures have shared the same mountain crossing for centuries, just in very different forms.