As the national capital, Washington, D.C. hosts about 185 foreign missions, including embassies, ambassador's residences, and international cultural centers. Many are concentrated along a stretch of Massachusetts Avenue known informally as Embassy Row. Washington, D.C., hosts a number of internationally themed festivals and events, often in collaboration with foreign missions or delegations. The city government maintains an Office of International Affairs to liaise with the diplomatic community and foreign delegations. D.C. has 15 official sister city agreements or protocols of friendship.