Former reservoir on hill to north-east of Fort Williamsburg is a Grade II listed building in the Gwynedd local planning authority area, Wales. First listed on 8 September 1998. Reservoir.

Former reservoir on hill to north-east of Fort Williamsburg

WRENN ID
rough-corner-martin
Grade
II
Local Planning Authority
Gwynedd
Constituency
Dwyfor Meirionnydd MP: Liz Saville Roberts (PC)
Country
Wales
Date first listed
8 September 1998
Type
Reservoir
Address
Former reservoir on hill to north-east of Fort Williamsburg, Glynllifon, Llandwrog
OS grid reference
SH 465 553
Coordinates
53.07329, -4.29185
Source
Cadw listing

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

Description

The former reservoir located on the hill to the north-east of Fort Williamsburg is a circular structure made of rubble. It features a deep ledge on the inner side that provides an access walk. The reservoir has outlets that lead into pipes, which feed into a cascade and grotto.

Local climate

Former reservoir on hill to north-east of 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.

More on this building

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Nearby listed buildings

  1. Rubble Footbridge uphill from Hermitage Grade II 350 m
  2. Rubble Footbridge below the Hermitage Grade II 383 m
  3. Hermitage Grade II 397 m
  4. Pair of Stone Bridges beside Iron Bridge and below Hermitage Grade II 432 m
  5. Iron Footbridge over Afon Llifon Grade II 445 m
  6. Stone Footbridge to north-east of the Fountain at the end of the vista Grade II 477 m
  7. Rubble Footbridge between Iron footbridge and Cave Grade II 547 m
  8. Barracks at Fort Williamsburg Grade II* 560 m
  9. Gatehouse at Fort Williamsburg Grade II* 564 m
  10. Armoury at Fort Williamsburg including attached screen walls Grade II* 568 m