Many clock towers are freestanding structures but they can also adjoin or be located on top of another building.
Some other buildings also have clock faces on their exterior but these structures serve other main functions.
Clock towers are a common sight in many parts of the world with some being iconic buildings.
Although clock towers are today mostly admired for their aesthetics, they once served an important purpose.
It included a display of the zodiac and the solar and lunar paths, and a pointer in the shape of the crescent moon that travelled across the top of a gateway, moved by a hidden cart and causing automatic doors to open, each revealing a mannequin, every hour.
[5][6] It was possible to re-program the length of day and night daily in order to account for the changing lengths of day and night throughout the year, and it also featured five robotic musicians who automatically play music when moved by levers operated by a hidden camshaft attached to a water wheel.
Line (mains) synchronous tower clocks were introduced in the United States in the 1920s.
The Abraj Al Bait, a hotel complex in Mecca constructed in 2012, has the largest and highest clock face on a building in the world, with its Makkah Royal Clock Tower having an occupied height of 494.4 m (1,622 ft), and a tip height of 601 m (1,972 ft).