These mysterious structures are littered all over Darka. They can mostly be found at the most north and south parts of the continent.
Purpose / Function
Nobody really know the reason these ruins were built. They seem to house many strange unexplained technology (Reports from the very few adventurers and researchers who made it in and out again) and the ruins themselves serve as complex vaults. They're super hard to get into due to Traps, puzzles, Traps, Traps and more traps. By the latest research, they seem to be research facilities themselves, with heavy fortifications to protect the information inside.
The ruins themselves seem to have pieces missing. Purposefully removed pieces that would otherwise seem important to the full functioning of some of these mysterious structures. I guess modern society will never ever know (Bastards...)
The architecture is very precise and simple, mostly made up of perfectly carved rectangles erected from the ground with some perfectly shaped pyramids surrounding it. The colours are typically a grey, or a cool dark green. The doorways are never perfect squares though, they have strange irregular angles. Nobody knows why that is since they are clearly advanced enough to make a proper doorway, but the entrances are at logical and predictable locations around the ruins.
Before the Elves, Orcs and other races inhabited Darka. A reptilian race ruled over the entire continent with the help of advanced beings who've come from the sky. This was more than thousands and thousands of years ago, but many of their structures and technology/Artefacts still remain to this day.