Museum Mile is the portion of Fifth Avenue that extends along Central Park. Billionaires built splendid mansions along the street, then, in the early 20C, many of them donated these properties to foundations. Hence this now being the stretch with the most exclusive private mansions in New York and one of the richest concentrations of museums in the world: the Frick Collection, the Asia Society and Museum, the Guggenheim Museum, the Cooper-Hewitt Design Museum, not to mention the MET!