The Unteres Schloss (Lower Castle) anchors the pedestrian centre of Siegen's old town. Its distinctive octagonal tower — the Kroenchen (little crown) — topped with a golden crown is the most recognisable landmark of the city, visible from a distance and frequently used as a symbol of Siegen. The castle complex houses government offices for the Siegen-Wittgenstein district, so the interior is largely inaccessible, but the exterior and the surrounding square make for a good orientation point.
The Kroenchen tower dates from the 16th and 17th centuries, though the castle's origins are older. The golden crown on top was added by the Nassau-Orange dynasty as a symbol of royal status. The adjacent Nikolaikirche (see separate entry) is closely related to the castle historically and architecturally. The square in front of the Lower Castle has been attractively laid out as a pedestrian zone with outdoor seating, and this is the social centre of old-town Siegen on a warm afternoon.