 The Centro remained the commercial, political and intellectual center through the mid 20th century although it was around this time that UNAM moved most of its facilities to the new Ciudad Universitaria.The reason for the decline of the city center was partly man-made and partly natural.In the 1940s, the city government froze rents so that until 1998 when the government repealed the law, tenants were still paying 1950's-level rents.