We'll collect responses from PiGu and Aj in this comment to make them easier for users to find.
Yes indeed! A very unique and beautiful monument
Yes they do! They work just like any other special building, so they can be properly interacted with and constructed : )
There's definitely more information in Tuesday's Dev Diary on this, but generally speaking they make full use of existing modifiers and mechanics without trying to reinvent the wheel. I tried to mostly keep them in line with those from the base game, design-wise.