Astronomische Uhr, Rathaus, Esslingen, Medieval astronomical clock at Old Town Hall in Esslingen, Germany

The Astronomical Clock at the Old Town Hall in Esslingen is a wrought-iron tower clock with an astronomical dial, built in 1581 and completed in 1589. Its lower dial shows the time with a large hour hand and a small minute hand, while the upper dial tracks the sun, moon and lunar nodes. Justitia and Temperantia stand on the cornice above.

The clock was created in 1581 by clockmaker Marx Schwarz and received significant improvements in 1586 from Jakob Diem, who enhanced the astronomical gearing system. These upgrades established the foundation for the device's precise operation across multiple centuries.

Every day at noon the clock's glockenspiel starts, driven by the restored 1589 movement. On the cornice above the astronomical dial stand the figures of Justitia, goddess of justice, and Temperantia, goddess of moderation. The clock was named Monument of the Month for March 2007 by the Denkmalstiftung Baden-Württemberg.

The clock is best viewed from the market square, where you can see the entire facade and hear the bell chimes clearly. Good viewing angles are also available from the steps and side streets of the Old Town that run around the Town Hall.

The astronomical dial is driven by the 1589 gear train, and an added correction gear means the displays will not need readjusting for the next 500 years. The clock also keeps time to about ±20 seconds thanks to a helper mechanism behind the medieval movement.