"structures of various shapes, all transparent and translucent."
"Dwellings have a hemispheric appearance, made of a crystalline substance, which makes them appear transparent. They have the property of an optical membrane – from the inside, one can see the entire surrounding space, and the insides from the outside cannot."
https://www.tachyontemple.com/post/light-cities-built-thousands-of-years-ago-from-earlier-3rd-and-4th-human-races
"these ‘cities of light’ have a particular quality – they are ‘crystalline’ – or more directly, made of transparent gold."
https://grahamhancock.com/gtaylor4/