The old town of Potsdam is composed of several well-defined quarters. The main axis of the second Baroque extension, once defined by a town wall, is Brandenburger Straße, which ends at the ostentatious Brandenburg gate. Two other gates of that enclosure still exist, Jägertor (hunters' gate, the oldest) and Nauener Tor, based on a sketch by Frederick the Great. Nauen gate actually is considered to have been the first Neo-Gothic structure on the European continent.