Please answer the following question: Information:  - Uruguay, officially the Oriental Republic of Uruguay, is a country in the southeastern region of South America. It borders Argentina to its west and Brazil to its north and east, with the Río de la Plata (River of Silver) to the south and with the Atlantic Ocean to the southeast. Uruguay is home to an estimated 3.42 million people, of whom 1.8 million live in the metropolitan area of its capital and largest city, Montevideo. With an area of approximately , Uruguay is geographically the second-smallest nation in South America, only larger in size than Suriname.  - Avenida 18 de Julio, or 18 de Julio Avenue, is the most important avenue in Montevideo, Uruguay. It is named after the date the first Constitution of Uruguay was written: July 18, 1830.  - The Americas, also collectively called America, encompass the totality of the continents of North America and South America. Together they make up most of Earth's western hemisphere and comprise the "New World".   - Puerta de la Ciudadela ( Gateway of the Citadel ) , or simply Ciudadela is one of the few remaining parts of the wall that surrounded the oldest part of the city of Montevideo , the citadel , which was torn down in 1829 . It is located by Plaza Independencia , in Ciudad Vieja .  - Plaza Independencia (Spanish for Independence Square) is the name of Montevideo's most important plaza. It separates Ciudad Vieja from downtown Montevideo, with the Gateway of The Citadel on one side and the beginning of 18 de Julio avenue on the other.  - Montevideo is the capital and largest city of Uruguay. According to the 2011 census, the city proper has a population of 1,319,108 (about one-third of the country's total population) in an area of . The southernmost capital city in the Americas, Montevideo is situated in the southern coast of the country, on the northeastern bank of the Río de la Plata.  - The Río de la Plata ("River of Silver")  rendered River Plate in British English and the Commonwealth and La Plata River (occasionally Plata River) in other English-speaking countries  is the river and estuary formed by the confluence of the Uruguay and the Paraná rivers. It empties into the Atlantic Ocean, forming a funnel-shaped indentation on the southeastern coastline of South America.    Given the information, choose the subject and object entities that have the relation of 'country'.
Answer:
ciudadela , uruguay