Central business districts, or CBDs, developed from locations where trading originally took place between communities. Over time, these trading places became permanent marketplaces and gathering spots for commerce. As business establishments grew around these centers to provide food, services, housing and more for travelers and merchants, it marked the beginning of what we now know as CBDs. Modern CBDs represent the economic heart of a city, housing most businesses, banks, transportation hubs and communication centers in high-rise office buildings and facilities.