Claire Brown's mind
Claire Brown's mind was the inner subconsiousness of psychic Claire Brown where a rogue Weeping Angel nested itself to protect itself from other Weeping Angels, specifically the Extraction Squad from Division that were attempting to capture it. Claire's mind resembled a beach, at first covered with sand and later with rocks.
The Thirteenth Doctor entered the mind to confront the Angel, offering to protect it against the Extraction Squad in exchange for the Weeping Angel leaving Claire's mind. The Angel agreed, but eventually went back on the deal, offering the Doctor to the Weeping Angels instead, who agreed to the trade, letting Claire's Angel go whilst turning the Doctor into a Weeping Angel. (TV: Village of the Angels)
The rogue Weeping Angel was later forced from Claire's mind and imprisoned by Tecteun. (TV: Survivors of the Flux)