Simplify the following text for a Grade 14 native English-speaking person.
Original: There is no official or commonly accepted definition of its area , but its characteristics are understood to include a high density built environment , high land values , an elevated daytime population and a concentration of regionally , nationally and internationally significant organizations and facilities .
Simplified: There is no official or commonly accepted definition of its area . Its characteristics are understood to include a high density built environment , high land values , an elevated daytime population and a concentration of regionally , nationally and internationally significant organizations and facilities .