Lopper, Mountain and archaeological site in Hergiswil, Switzerland

Lopper is a mountain with steep slopes dropping roughly 500 meters to Lake Lucerne and Lake Alpnach on both sides, reaching 961 meters in elevation. The mountain holds archaeological importance and is recognized as a cultural property of regional significance.

In 1848, the Swiss federation supported construction of the first road around Lopper to connect isolated mountain regions and create new passages through the mountains. Tunnel construction followed later in the 20th century, fundamentally changing how people could reach this area.

The Lopperkapelle on the eastern slope above the Acheregg was built in 1964–1965 by the family of Hergiswil industrialist Alfred F. Schindler and donated to the canton of Nidwalden. The family gave it as thanks for the Loppertunnel and Acheregg bridge works and that no one was seriously hurt during construction. It was renovated in summer 2022 and is usually closed from November to April.

The cantonal road between Hergiswil and Stansstad still runs along the unstable north flank, protected by a gallery; a rockfall closed it on 12 October 2009, and from March 2010 to May 2011 a 500-metre pontoon bridge carried single-lane traffic. The Lopper chapel above the Acheregg is usually closed from November to April.

The Lopper chapel was built in 1964–65 by the family of Hergiswil industrialist Alfred F. Schindler and donated to the canton of Nidwalden as thanks that no one was seriously hurt during construction of the Loppertunnel and Acheregg bridge. It is usually closed from November to April.