17.7791°N, 89.2800°W.
Rio Azul is an Early Classic Maya city in the extreme northeast Peten of Guatemala, near the border with Mexico and Belize, occupied principally between approximately 250 and 530 CE. The site was a strategic trade and military node at the headwaters of the Rio Azul, controlling the route between Tikal to the south and the Petexbatun and Calakmul polities. The city is best known for Tomb 1, a stone-lined burial chamber sealed in 417 CE containing the body of a Tikal-affiliated lord and a set of cylindrical lidded vessels — one of which carried glyphic labels identifying its contents as kakaw, providing the earliest direct chemical confirmation of Maya cacao consumption when residue analysis at Hershey Foods in 1990 detected theobromine and caffeine. Richard Adams directed the University of Texas project that excavated the looter-damaged site in the 1980s.
The Tomb 1 walls were painted with bright red glyphic friezes naming the principal ancestors of the buried lord.