The Guayabo National Monument is located to the northwest of the city of Turrialba, Santa Teresita district, Cartago province. The archeological site is located on approximately 20 hectares of the protected area. This part consists of a group of pre-Hispanic architectural structures made of stone – rounded river stones – which were built over a period ranging from 1000 BC to 1400 AD, indicating a prolonged occupation of some 2,400 years. The wildlife area, consisting of 233 hectares, protects a remnant of evergreen premontane rainforest which extends over an elevation range of 990-1,300 meters above sea level with an annual average temperature of 24°C. The United States Association of Civil Engineers, one of the leading organizations in this area worldwide, has accorded Guayabo National Monument the status of World Heritage in Civil Engineering. This designation recognizes the engineering achievements and techniques used by the first inhabitants of the Guayabo National Monument, which have endured to the present day.