There are 33 Grade I listed buildings in West Somerset . The oldest is either Culbone Church , one of the smallest churches in England , and pred @-@ Norman in origin , or Tarr Steps , which may originate in the Bronze Age , although other sources date them from around 1400 . Dunster have the greatest concentration of Grade I listed buildings , including Dunster Castle , which was built in 1617 on a site which had supported a castle for the previous 600 years ; the Yarn Market , which was built in 1609 ; Gallox Bridge , which date from the 15th century and the Priory Church of St George which is predominately from the 15th century but include part of the earlier church on the same site . Other sites include manor houses such as the medieval buildings at Nettlecombe Court and Orchard Wyndham .