All 3 of the other commenters are replying without having done any actual thought or research. The paper repeatedly references MatrixCity and another commenter

All 3 of the other commenters are replying without having done any actual thought or research. The paper repeatedly references MatrixCity and another commenter above found this https://city-super.github.io/matrixcity/ https://city-super.github.io/matrixcity/ which also, I'd like to add, calls out that it's fully Synthetic. And, from what I understand, is extracted from Unreal Engine.