 In addition to courts , and now a gaol , Chester Castle also housed a garrison of soldiers . The forecourt of the Shire Hall formed a parade ground for the garrison , and Harrison designed two new buildings for the soldiers . On the west side of the parade ground he built an Armoury , and on the east side a matching block , with more utilitarian buildings behind , to act as the Barracks . Both of the blocks consists of a two @-@ storey building in nine bays , the fronts of which are decorated with Ionic half @-@ columns about 23 feet ( 7 m ) high . Harrison 's final building in the complex was a monumental gateway or Propylaea at the entrance to the forecourt . This consists of a central block , with two lateral pavilions that originally served as guardhouses . The central block has a portico extending some 10 feet ( 3 m ) in front of the pavilions , with a double colonnade of four Doric monolithic columns standing 18 feet ( 5 m ) high . Above them is a triglyph frieze , and a low attic . The pavilions are lower than the central block , and decorated at their front with two Doric half @-@ columns between pilasters . At the back the pavilions project 10 feet ( 3 m ) beyond the central block and have four Doric columns . The structure , which was built between 1813 and 1815 , contains 22 monolithic columns . 
