One of the more unusual clocks I’ve seen in some time (pun intended) is the World Time Clock (Weltzeituhr) in Berlin’s Alexanderplatz. It was constructed in former Communist East Berlin in 1969 (and restored in 1997, after reunification). It weighs 16 tons and is 10 meters tall.
The design is simple but engaging. The clock has a rotating numerical time dial and a fixed cylinder with the world’s 24 time zones, with main cities in each zone outlined. You can see what the time in your favorite city is when you visit, or just enjoy the unusual Soviet-influenced design, including a rotating solar system above the clock.