Here is a dark city scene setup with emissive materials for the windows and emissive spheres used as street lamps (EEVEE)
As you noticed, the emissive lights do not cast light on the surrounding objects - to do this in EEVEE, you will need an Irradiance Volume. Scale the Volume to your size requirements and bake the lighting in the render properties tab. You can adjust the cube-map size if you need better resolution (right side)::
You can also select the Irradiance properties and change the resolution - don't go too high or performance will suffer:
Here is the scene after the bake - the lighting will stay the same until you bake delete the lighting cache or bake again:
