Both are commonly used. However, if you want to emphasize the ownership of the lights, use " city's ".
Use city lights. The cases where "city's lights" might be better are very specific, dealing with comparison to another place's lights.
las Vegas
city life style
land pollution is a major problem of a big city
opening the door mother went in her home office turned on the lights and then the theft was discovered by her. I would leave out the passive part -- the theft was discovered by her -- and write it as past simple. I would write the whole sentence as past simple. Mother opened the door, went into her home office, turned on the lights and discovered the theft.
A paragraph on The Hazards of City Life can include the advantages and disadvantages to big city living. You can also compare city life to rural life.
"Citys" is an incorrect plural form of "city." The correct plural form is "cities."
jor
Gods of citys
Satellite cities.
Atlanta IS a city, what is your question
kansas city
specify what city you know how many citys there are ?
Pretty Much, any city that is inland.
Seattle
Oklahoma City, Tulsa, and Norman
One of the citys near the equater.
Denver is considered a major city.