Caernarfon is the traditional county town of the traditional county of Caernarfonshire and was a county corporate in its own right. The town is best known for its great stone castle, built by Edward I of England and consequently sometimes seen as a symbol of English domination. Edward's architect, James of St. George, modelled the castle on the walls of Constantinople, possibly being aware of the alternative Welsh name Caer Gystennin; in addition, Edward was a supporter of the Crusader cause. On higher ground on the outskirts of the town are the remains of an earlier occupation, the Segontium Roman Fort.
Caernarfon is also home to the regimental museum of the Royal Welch Fusiliers (archaic English spelling of the word Welsh).
Caernarfon railway station in St. Helen's Road is the northern terminus of the narrow gauge Welsh Highland Railway. Caernarfon was at one time an important port, exporting slate from the Nantlle Valley quarries. Caernarfon Airport is 4.5 miles to the south west, and offers pleasure flights and an aviation museum..
Caernarfon has a small harbour and a Blue Flag beach at Victoria Harbour.