Switzerland's largest lake-shore town on the Bodensee, Kreuzlingen sits directly on the border with the German city of Konstanz — the two towns are joined by a pedestrian crossing, and the easiest way to feel the geography is to walk it. The old town of Konstanz is just across the line; the Swiss customs office sits in the middle of what is functionally a single street.
Kreuzlingen itself is small, modern, and largely an industrial-and-shopping satellite of Konstanz, but the harbour and the Seepark are pleasant, and the Saturday market on the Hauptstrasse is good. The town is the eastern terminus of the Mittelthurgau railway and the natural base for cycling the Untersee toward Stein am Rhein.