What is a ruin? We're running off of "You know it when you see it" at the moment. Ruins should be non-functioning structures of some age, or their function reduced to tourism and the like. Generally speaking, specific items from a ruin should go to [email protected] Illustrations of ruins (or their reconstructions) should go to [email protected] Photos of ruins back when they were functioning should go to [email protected]
The architectural importance of this gate and the tomb of Clytemnestra nearby, is that they are not true arches but corbel arches. True arches were invented not much later, the oldest still standing true arch bridge is also built by Mycenaeans, the Arkadiko Bridge .
https://en.wikipedia.org/wiki/Arch#Bronze_Age:_ancient_Near_East