Blender 2.8 particles scale is off Particles do not have the same scale as the objects from the collection they're created from: 

They're much smaller: 




The particles were assigned to a plane but appear outside of it as well:



I've played around with the scale and got them to the original intended size but the buildings were also spaced out outside the plane.
Like @stphnl329 says apply the scale of all particle objects, then go to the render settings of your particle system. For some reason the default scale is  0.05, change that to 1