The City of San Marino, also known simply as San Marino and locally as Città, is the capital city of the Republic of San Marino and one of its n…The City of San Marino, also known simply as San Marino and locally as Città, is the capital city of the Republic of San Marino and one of its nine castelli. It has a population of 4,061. It is on the western slopes of San Marino's highest point, Monte Titano. It is also the fifth-least-populated national capital in the world.