The microscale urban climate model PALM-4U (i.e. PALM for Urban applications) is based on the PALM model and can be run in both LES (Large Eddy Simulation) and RANS (Reynolds Averaged Navier–Stokes) mode. Within the joint project MOSAIK (Model-based city planning and application in climate change), an online chemistry model has been implemented into PALM-4U, including both gas-phase and aerosol chemistry. In this study, we have set up PALM-4U for a nested simulation for a city quarter of Berlin with a ‘parent’ domain on 10 m grid resolution and a ‘child’ domain, which is a cut-out of the ‘parent’ domain, on 1 m grid resolution. For the simulation a real-time traffic emission data set has been used. The model results for both, the ‘parent’ and the ‘child’ domain are presented.