Zurich

Zurich has the shortest ride on the list: direct trains from the station below the airport reach Zurich HB in roughly 10 to 12 minutes, and they run all day long. That makes even a four- or five-hour gap realistic. From the main station, walk up the Bahnhofstrasse toward the lake, then cut into the old town on either side of the Limmat, where the twin towers of the Grossmünster and the lanes of the Niederdorf fill an hour or two. Prices are steep, so this is a city for walking and looking rather than long lunches. Swiss punctuality makes the return journey the most predictable on this list.