Grotto in Gnoll Estate is a Grade II listed building in the Neath Port Talbot local planning authority area, Wales. First listed on 25 February 2000. Grotto.
Grotto in Gnoll Estate
- WRENN ID
- swift-keystone-cream
- Grade
- II
- Local Planning Authority
- Neath Port Talbot
- Constituency
- Neath and Swansea East MP: Carolyn Harris (Lab)
- Country
- Wales
- Date first listed
- 25 February 2000
- Type
- Grotto
- Address
- Grotto in Gnoll Estate, Tonna
- OS grid reference
- SS 780 980
- Coordinates
- 51.66831, -3.7649
- Source
- Cadw listing
Description
The Grotto in Gnoll Estate is a Grade II listed structure cut into bedrock beneath a rebuilt gazebo. The entrance features a large bedrock lintel and is flanked by drystone revetment walls, designed to resemble a prehistoric chamber tomb in the Cotswold-Severn style. Inside, there is a single circular chamber quarried from bedrock, topped with a crude flattened domical stone vault that was meant to drip lime and form stalactites. The floor consists of an outer circular pavement made of random paving stones, with a kerb that likely marks the location of a former pool in the center.
Local climate
Grotto in Gnoll Estate sits in one of the wettest parts of the UK, with an average of 1,380 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 96% of listed buildings.
It experiences an average of 28 freeze-thaw cycles a year, fewer than 69% of listed buildings. Of these, 12 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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- No EPC on record for this property
- No sale records on file
- No related consent applications matched
- Detailed attributes — period, style, materials, features
- Flood risk assessment
- Radon risk assessment
- Weather exposure and heating demand — rain and frost month by month and year by year, wind direction, solar and humidity
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