Beaumaris Castle

Begun in 1295 on flat marshland, Beaumaris was the last and most symmetrical of Master James of St George's castles, laid out as a perfect square within a square with four concentric lines of defence, a moat filled from the sea, a dock where ships could tie up at the wall, and no natural high ground to compromise the geometry. It was never finished: costs ran beyond what the crown would pay, work stopped and started for decades and the towers stand at about half their intended height with no upper storeys, so a visitor walks a plan rather than a building. That incompleteness makes the design unusually legible, since every element of the intended defence is visible at once. It is part of the UNESCO group inscribed in 1986. The town outside has a Georgian gaol and courthouse.

What you actually see

• The perfect symmetry - a square castle within a square, on flat ground.
• The unfinished towers - walls stopped at roughly half their planned height.
• The tidal dock - a channel where supply ships tied up at the wall.
• The legible plan - four concentric defensive lines all visible at once.

When to go

April to October for full opening; the site is low-lying and exposed and the moat area is muddy after rain. Winter hours are reduced. Anglesey's coast path passes close by.

Honest expectations

Because it was never completed, there is no height to climb and no roofed interior, so it can feel flat compared with Caernarfon or Conwy. The moat is partly silted. The site is small and a visit is short.

Nearby

The Menai bridges lie southwest; Anglesey's coast path runs past the town.