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Link for a detailed description of Conwy castle and walls.

Link for a guided tour of the walls. (Conwy.Wales.com)

Conwy castle is one of the most picturesque of Welsh castles and a masterpiece of medieval military architecture. The castle and town walls are now in the UNESCO World Heritage List as a site of outstanding universal value. They were built by Edward I between 1283 and 1289 and helped to complete the conquest of the Welsh princes in North Wales. In Conwy, the castle's commanding position on a rocky outcrop overlooking the estuary dictated its very size and shape and gave it its great military strength. Taken together the castle and the town walls of Conwy, planned as a single unit, are the most impressive of all the fortresses built by King Edward I. Over 1.2 km. long, the town walls defended the largest of Edward's Welsh frontier towns with their 21 towers and 3 gateways. The town walls also acted as the outermost defences of the castle, an imposing compact eight-towered stronghold surrounded by water on three sides. Nearest the town, the castle's own outer bailey housed the garrison, then, doubly defended by town wall and the outer bailey, came the king's private apartments in the castle's inner bailey. It is one of a ring of castles built by Edward I around Wales.
Grade I listed. Link

In the United Kingdom, a scheduled monument is a 'nationally important' archaeological site or historic building, given protection against unauthorised change.
There are about 20,000 scheduled monuments in England representing about 37,000 heritage assets. Of the tens of thousands of scheduled monuments in the UK, most are inconspicuous archaeological sites, but some are large ruins.
Wikipedia: Link