A central business district (CBD) is the commercial and business center of a city. It contains commercial space and offices. In larger cities, it is often synonymous with the city's "financial district". Geographically, it often coincides with the "city center" or "downtown", but the concepts are not mutually exclusive: many cities have a central "business" district located away from its commercial and or cultural center and or downtown/city center, or even several CBDs at once. For instance, London's city center is usually regarded as encompassing the historic City of London and the medieval City of Westminster, while the City of London and the transformed Docklands area containing Canary Wharf are regarded as its two respective CBDs. In New York City, Midtown Manhattan is the largest central business district in the city and in the world. In Chicago, the Chicago Loop is the second largest central business district in the United States and in the world. It is also referred to as the core of the city's downtown. Mexico City also has its own historic city center, the colonial-era "Centro Histórico," along with two CBDs: the mid-late 20th century Paseo de la Reforma – Polanco, and the new Santa Fe, respectively. Moscow and Russia's largest central business district is the Moscow International Business Center.