Eastgate and Eastgate Clock in Chester, Cheshire, England, stand on the site of the original entrance to the Roman fortress of Deva Victrix. It is a prominent landmark in the city of Chester and is said to be the most photographed clock in England after Big Ben.
The original gate was guarded by a timber tower which was replaced by a stone tower in the 2nd century, and this in turn was replaced probably in the 14th century. The present gateway dates from 1768 and is a three-arched sandstone structure which carries the walkway forming part of Chester city walls. In 1899 a clock was added to the top of the gateway to celebrate the diamond jubilee of Queen Victoria two years earlier. It is carried on openwork iron pylons, has a clock face on all four sides, and a copper ogee cupola. The clock was designed by the Chester architect John Douglas. The whole structure, gateway and clock, was designated as a Grade I listed building on 28 July 1955.
More information at: http://en.wikipedia.org/wiki/Eastgate_and_Eastgate_Clock