The station is an example of late-Victorian Romanesque Revival architecture and is highly castellated. The tower originally contained an early mechanical digital clock; when replacement French silk drive belts proved unavailable during World War I, it was replaced by a traditional analog clock. The tower was originally topped by a bronze statue of the Roman god Mercury; this was toppled in a storm in 1951. When a new Main Post Office was built in Nashville in 1935, it was located adjacent to Union Station. A connecting passageway between the two served to transport mail to and from trains for over three decades.