Siebenzwingstein, Boundary marker in Aargau, Switzerland

Siebenzwingstein is a boundary marker made of interlocked granite blocks positioned at 607 meters elevation where the municipalities of Gränichen, Teufenthal, and Seon meet. The site also marks the convergence of the Lenzburg, Kulm, and Aarau district boundaries.

The stone marks where seven Zwinge once met, judicial districts each grouping several villages under a common court: Teufenthal, Dürrenäsch, Retterswil, Seon, Gränichen, Liebegg and Trostburg. Retterswil was absorbed into Seon in 1898, Liebegg passed to Gränichen and Trostburg to Teufenthal, and Dürrenäsch no longer reaches the stone. Why these borders met at an indistinct spot in the Liebeggerwald is unexplained.

The name comes from the seven Zwinge, judicial districts that once met here, each grouping several villages under a common court: Teufenthal, Dürrenäsch, Retterswil, Seon, Gränichen, Liebegg and Trostburg. The stone is also called Sibe Zwingstei on maps. Visitors can spot the interlocked granite blocks that mark the tripoint of Gränichen, Teufenthal and Seon.

The stone lies in the Liebeggerwald forest, on the municipal boundary of Gränichen, Teufenthal and Seon, at 607 m above sea level. Approach on foot through the forest; the exact spot is hard to define, so follow the boundary line rather than expecting a signposted viewpoint. Coordinates 47°20′4.9″N, 8°8′34.6″E (CH1903: 653234 / 242888).

The name refers to seven Zwinge, judicial districts that once met here; today only three municipalities do. Dürrenäsch no longer reaches the stone for unexplained reasons, and Liebegg and Trostburg were absorbed into Gränichen and Teufenthal. Retterswil was merged into Seon in 1898. Why all these borders met at a hard-to-define point in the Liebeggerwald is still unexplained.