 In contrast with Lancaster , Harrison was able to prepare an organised plan for the gaol , as it was to be built on a new site behind the Elizabethan Shire Hall on land sloping down to the River Dee . Also in contrast to Lancaster , the buildings were to be in Neoclassical style . The Gaoler 's House would stand behind the Shire Hall , overlooking the exercise courtyards . Inside the semi @-@ octagonal perimeter wall of the site would stand two @-@ storey blocks to house the prisoners . The site was staked @-@ out in November 1786 , but nothing could be done until the necessary Act of Parliament was passed the following July . Work started on the prisoners ' accommodation early in 1789 and on the Goaler 's House in early 1792 , and was completed two years later . Plans were then put in place for a new Shire Hall to replace the Elizabethan building , which was completed in 1802 . The Shire Hall was another structure in which Harrison made innovations , in this case the use of Greek architectural motifs . Its façade is about 250 feet ( 76 m ) long and 25 feet ( 8 m ) high , in nineteen bays with two storeys . At its centre is a Doric @-@ style portico with twelve columns , projecting forwards by about 10 feet ( 3 m ) . Its interior contains a semi @-@ circular courtroom with a diameter of 80 feet ( 24 m ) . Its curved wall has a colonnade of ten Ionic columns , and on each side of the judge 's bench are two similar columns . The room has a coffered semi @-@ dome . 
