 Other than the smaller bridges , almost all the structures designed by Harrison have been designated as listed buildings by English Heritage , Cadw , or Historic Scotland . Some of the buildings he completely designed ( rather than altered ) have been listed at the highest levels , Grade I in England and Wales , and Category A in Scotland . Grade I includes buildings that " are of exceptional interest , sometimes considered to be internationally important " ; only 2 @.@ 5 % of listed buildings are in this Grade . Category A consists of " buildings of national or international importance , either architectural or historic , or fine little @-@ altered examples of some particular period , style or building type " , and includes about 8 % of the Scottish listed buildings . These structures are , in Chester , Grosvenor Bridge , and Northgate , and in Scotland , the Mausoleum at Gosford House , and Colinton House . Lancaster Castle as a whole is listed at Grade I , and at Chester Castle four of Harrison 's buildings are listed separately at this Grade : the main block containing the Shire Hall , the Propylaea , and the two blocks flanking the forecourt . 
