The adjective sprawling is good for describing things that extend across a large area. You could describe your school as sprawling if it consists of many buildings spread over several acres.
It's pretty common to hear a city or its suburbs described as sprawling, since some cities tend to grow that way, spreading their populations out over a large amount of land. You can also describe your brother as sprawling if he likes to sit stretched out on the couch, taking up more than his share of space. The verb sprawl is at the root of sprawling, and it comes from an Old English word, spreawlian, "move convulsively."