The Central Business District (CBD) is the commercial, cultural, and transportation center of a city. It faces competition from internet shopping, retail parks, and huge out of town supermarkets and business parks. As a result, some CBDs have experienced decline with empty shops and offices moving to the outskirts of cities. To revitalize the CBD, cities can pedestrianize areas, bring empty buildings back into use, improve safety and security, create a nicer environment, and hold special events to attract people back into the center.