Grange Cavern Military Museum - Wales
The former Grange Cavern, once a wartime arms store and later a major underground museum, now lies silent after its scattered collection and unresolved missing artefacts.
Cefn Coed Colliery Museum - South Wales
Once the world’s deepest anthracite mine, this former colliery became a museum but has been closed since 2021 due to major structural and safety issues.