Outer Defensive Wall to Fort Williamsburg is a Grade II* listed building in the Gwynedd local planning authority area, Wales. First listed on 29 May 1968. Defensive wall.

Outer Defensive Wall to Fort Williamsburg

WRENN ID
nether-landing-brook
Grade
II*
Local Planning Authority
Gwynedd
Constituency
Dwyfor Meirionnydd MP: Liz Saville Roberts (PC)
Country
Wales
Date first listed
29 May 1968
Type
Defensive wall
Address
Outer Defensive Wall to Fort Williamsburg, Glynllifon, Llandwrog
OS grid reference
SH 460 550
Coordinates
53.07019, -4.29896
Source
Cadw listing

Also on this page: flood risk · radon risk · weather exposure · detailed attributes ↓

Description

The Outer Defensive Wall to Fort Williamsburg is a Grade II* listed structure. It is made of roughly coursed rubble and is partly overgrown. The wall outlines a roughly square boundary around the star-fort and features angled bastions, or redans, at each of the four corners, serving as an outer defense flanked by ditches. There are arched entrances with gates on all four sides, with the main entrance located to the north through the gatehouse. To the south, the wall is interrupted by modern farmyard buildings, next to which is a tunnelled gateway that leads into the barracks. The fort itself is roughly square, with redans at the corners and surrounded by ditches and revetment walls.

Local climate

Outer Defensive Wall to Fort Williamsburg sits in one of the wettest parts of the UK, with an average of 1,370 mm of rain a year. This makes it wetter than 97% of listed buildings in the UK. Its exposure to wind-driven rain is greater than that of 98% of listed buildings.

It experiences an average of 20 freeze-thaw cycles a year, fewer than 78% of listed buildings. Of these, 9 follow at least 1 mm of rain in the preceding 48 hours. Average temperatures at this location have risen by 0.3°C per decade since 1991.

Averages for 1991–2020; temperature trend 1991–2025. Figures describe the wider area (a grid cell of roughly 10 km), not the individual site. Contains modified Copernicus Climate Change Service information 2026.

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Nearby listed buildings

  1. Barracks at Fort Williamsburg Grade II* 35 m
  2. Armoury at Fort Williamsburg including attached screen walls Grade II* 41 m
  3. Tunnel Passage at Fort Williamsburg Grade II* 95 m
  4. Gatehouse at Fort Williamsburg Grade II* 96 m
  5. Tower at Fort Williamsburg Grade II* 108 m
  6. Magazine at Fort Williamsburg Grade II* 114 m
  7. Cascade at Glynllifon Grade II 327 m
  8. The Mill Folly Grotto including stone bridge, south of the Afon Llifon Grade II 346 m
  9. Fountain at end of east vista Grade II 348 m
  10. Eastern Cavern north of the path near main east vista fountain Grade II 373 m