capitals can be in cities that are already there like athens or rome, or a new town can be built and made the capital like canberra and alexandria. countries can change capitals from time to time. several cities have been the capital of china. the united states once had its capital in philadelphia and later in new york city but moved to the new city of washington, d.c. in 1800. rio de janeiro was the capital of brazil until the new city of brasilia was built between 1956 and 1960.