Random3Dcity is a basic and experimental procedural modelling engine that is focused on constructing buildings in multiple LODs and in CityGML.
A sample dataset (CityGML and OBJ) containing 900 buildings in multiple LODs can be obtained from here.
The methodology is described in the paper below. If you plan to use the dataset to make a nice publication please cite the paper.
Biljecki F, Ledoux H, Stoter J (2016): Generation of multi-LOD 3D city models in CityGML with the procedural modelling engine Random3Dcity. ISPRS Ann. Photogramm. Remote Sens. Spatial Inf. Sci., vol. IV-4/W1: 51-59. PDF