Klettgau
It is the centre of the "Klettgau" historical region stretching across the Swiss border into the cantons of Aargau , Schaffhausen and Zürich . 
<triplet> Swiss <subj> Aargau <obj> contains administrative territorial entity <subj> Schaffhausen <obj> contains administrative territorial entity <subj> Zürich <obj> contains administrative territorial entity <triplet> Aargau <subj> Swiss <obj> country <subj> Zürich <obj> shares border with <triplet> Schaffhausen <subj> Swiss <obj> country <subj> Zürich <obj> shares border with <triplet> Zürich <subj> Swiss <obj> country <subj> Aargau <obj> shares border with <subj> Schaffhausen <obj> shares border with