Cats unlike dogs are not about the amount of room you give them. I have two cats and they have moved with me from a house with a HUGE two acre area filled with trees and even a bunny for a best pal, to living in SF city medium sized shared-apartment completely indoors to now living in a small 1 bedroom. And they are completely happy and healthy - about to turn 14 years old.
For cats it is attention and control depending on their temperment. They love to rule what ever the size of the domain. And just give them plenty of toys, hell lately for my cats their favorite thing isn't the dozens of store bought "cat things" around but the plastic doo-hickey pulltab thing from the lid of a gallon of milk and a sock they stole from my laundry basket. They bat those things around the house and hunt them as if they were mountain lions. It is hysterical, because of course if the garbage truck comes and makes too much noise they run and duck under the bed, yup them's my rough tough huntin mountain lions.