The bell and drum were originally used as musical instruments in China. Afterward, however, they were used for telling time. As early as in the Han Dynasty (206 BC-220), there was 'a morning bell and a dusk drum'. Telling the time by bell and drum played an important role in helping people live and work regularly when there was no other means to keep track of the time. As a result, bell and drum towers became public architectures, and were widely constructed in almost every city throughout the country since the Han Dynasty. In the history of their construction, the bell and drum towers of Beijing are the largest and highest. Their layout is unique, in that they were placed fore-and-aft, not as the traditional sense of standing right-and-left horizontally.