Known as the Bönn Stadtbahn, the public transport network of the city of Bonn is an extension of the vast network of Cologne Stadtbahn, with two lines, 16 and 18, that link both cities. This network serves Bönn and the surrounding area and consists of a system of integrated Metro (rapid transit subway - Stadtbahn) complemented by: S-Bahn tram, U-Bahn subway and regional trains (DB). The Bönn Stadtbahn, consists of six lines, ...
Beautifully designed Kiev Metro Route Map from Kiev.com
Look at this amazing metro map from Shanghai. Their system is now longer than New York's and they only started building it a few years ago!