See if a city is available in Sketchup and model it yourself.  

look at neom, it's easy.

This depends on your time / skills / and use of the project

m any city models exists and are available to purchase,
you can pull line work from GIS. this usually takes a while but there ae tutorials. then clean up linework to your needs, and extrude the buildings to a certain standard height. 
you can sometimes pull geometry from goolgle earth
or trace the major roadways from a google maps screengrab.

again, i don't know your skills. but if you put you head down and just model away for 2-3 days you can create the thing. 

We built our city on rock and roll...

you can download 3d models of most cities in the world. Cant recall the site where the models are found, but google is your friend.  If a big enough city there is probably a government sponsored version of the city ready for download as well. 

If the city you want to model is entirely new and conceptual you can look at city engines. They are used for video games but the result is somewhat randomized, so it's not so much conscious design. 

Try Enscape

I don't know if you've worked with Blender, but there are a few plug ins. 

This comes to mind https://blender-addons.org/blo... I tried something like this for importing landscapes. Textures would stretch over mountains and cliffs etc...and in large scenes you could see where the scans were done in different seasons or at different qualities. 

Also, there's this, but I haven't looked too far into it;