https://www.andrewgrantham.co.uk/soundmirrors/locations/deng... is quite a good article and set of photographs about the Denge sound mirrors.

There are also some more accessible, but smaller, ones along the cost at https://beyondthepoint.co.uk/sound-mirrors/

Note "The only way of seeing the Denge sound mirrors close up is during one of the public open days run by the RSPB. There is no public access to the Dungeness mirrors, which are in the middle of a disused gravel pit. Contact the RSPB for the dates of future open days."