This notion has been challenged since the late 20th century by discoveries of monumental architecture from that period, such as an altar in La Blanca, San Marcos, from 1000 BC; ceremonial sites at Miraflores and Naranjo from 801 BC; the earliest monumental masks; and the Mirador Basin cities of Nakbé, Xulnal, El Tintal, Wakná and El Mirador.