Guayabo National Monument, located northwest of Turrialba in Costa Rica, is an archaeological site featuring pre-Hispanic architectural structures made from river boulders. These structures were built between 1000 BC and 1400 AD, reflecting a prolonged occupation of approximately 2400 years. The site also protects a remnant of pre-montane evergreen rainforest. The first reports of the archaeological site were conducted in 1886 by naturalist Anastasio Alfaro.