Schengen is a lovely and cute little village on the banks of the rivel Moselle in Luxembourg, about 15-20 mins from Luxembourg city. It has about 3,500 inhabitants, many of whom work in the vineyards that stretch all along the Moselle valley, producing small quantities of very under-estimated white wines (mostly Riesling, Pinots of all shades, Gewürztraminer). There are some nice restaurants there, I can amongst others recommend the "Chateau de Schengen".

Schengen used to be the place where one would cross the river Moselle to go to Saarbrucken. This process is made much easier these days by a relatively recent motorway going straight from Luxembourg to Saarbrucken. A long tunnel goes underneath the hills with the vineyards.

Schengen is also a stop for little cruise ships going up and down the Moselle, and one day the leaders of some European countries sat down on such a ship to sign a treaty that would abandon all passport and customs controls among member states.

If such a thing as a "Group of cities whose names have become the equivalent for something else better known than the City itself" existed, Schengen would be a member, alongside Waterloo, Yalta and Bretton Woods.

Hope that helps.... or is it off topic?