The castle respectively the tower is situated at the then only bridge over the Linth river, in the east of the former, dried up Tuggenersee lakeshore, at the southern end of the Buechberg hill in the municipality of Tuggen in the canton of Schwyz in Switzerland.

[1] Thereafter, the castle was sold by the sons of Count Johann I (among them Johann II von Rapperswil) around 1343/47 to Friedrich V von Toggenburg,[2] but after the extinction of the House of Rapperswil, in 1436/37 the property including all rights – especially the bridge toll – passed to the Old Swiss Confederacy; it was claimed by the canton of Schwyz, to control all traffic between the Eastern and Central Switzerland, as well as between the city republic of Zürich and the Gotthard Pass.

The transfer is valid "zuo stund" (now), and the inhabitants of the territories have to swear to the people of Zürich until next Hilariustag (13 January 1437); the Countess maintained all servitudes by lifetime.

[3] On 16 February 1437 Elisabeth von Matsch granted the mayor and council of the city of Zürich or their representatives the authority to act on their behalf, immediately after the usurpations of lands of the Toggenburg County by the cantons of Schwyz and Glarus, and to lock Grynow.

Again in 1833, Swiss federal troops were concentrated at the Grynau castle, on occasion of the then planned division of the canton of Schwyz, however, waived without an armed intervention.

And again in a Swiss civil war, the so-called Sonderbundskrieg, federal troops crossed the important bridge in March 1847, without a single dead soldier on both sides.