Installed in 1410, the world's oldest astronomical clock, still in operation, is called the Orloj and is in Prague, capital of the Czech Republic.
The Orloj is mounted on the southern wall of thein the . The clock mechanism itself has three main components:
1. The astronomical dial, representing the position of theand in the sky and displaying various astronomical details
2. Statues of variousstand on either side of the clock; "The Walk of the Apostles", a clockwork show of figures of the and other moving sculptures, notably a figure of (represented by a skeleton) striking the time.
3. A calendar dial with medallions representing the months.
The oldest part of the Orloj, the mechanical clock and astronomical dial, dates back to 1410 when it was made by clockmaker
I've actually seen the clock in person when I was in Prague, it was beautiful, a wonderful marriage between engineering and art.
Further Info: https://en.wikipedia.org/wiki/Prague_astronomical_clock