Schleithal
This boundary is defined by the Lauter which gives its name to the small town of Lauterbourg located at the mouth of the river Rhine . 
<triplet> Lauter <subj> Rhine <obj> mouth of the watercourse <triplet> Lauterbourg <subj> Rhine <obj> located in or next to body of water <triplet> Rhine <subj> Lauter <obj> tributary