The Maya city of Yaxchilan is sited within a giant omega of the Usumacinta River. This circular bend in the river developed a 3.2 kilometer wide land mass within the inner curve of the river. This protected area, formed within the confines of the inner curve of the river, created a natural fortress for the city. However, the river is in a flood state for six months of the year, and during the rainy season the broad and swiftly flowing waters isolated the city from access to its domain across the river
In order to survive as a viable urban center, this ancient city required a dependable year-round way to cross the river. While the site had been studied by archaeologists since 1882, the need for a bridge crossing was not considered as a necessity by archaeological studies. The ancient ruins that were the clues to the existence of this lost landmark of Maya Engineering were hiding in plain sight (see picture on right). The need for a permanent lifeline to insure the survival of the city during the flood season was overlooked by archaeologists until James O'Kon carried out a series of expeditions, forensic engineering investigations, archaeo-engineering analysis, remote sensing, and computer modeling of this structure lead to the digital re-construction of the bridge. Constructed in the late 7th century, landmark three-span suspension bridge crossed from the city center over the Usumacinta River to the north side where the villages and farms were located.
The rendering of the bridge indicates its design that supported the deck from shore to shore. The two tall bridge piers were located in the river with abutments on each bank. The geometry of the bridge extended 113 meters in three spans from the grand plaza of the city to the northern shore; the center span was 63 meters long.
The bridge construction consisted of a wooden deck suspended from rope cables made from henequen, a common Maya construction material. The cables spanned between cast-in-place concrete and stone towers topped by a Maya arch. The three-span bridge structure was elevated 22 meters above the river at low water levels. The height of the deck was established by the elevation of the approach structure, Structure 5, on the Grand Plaza. This elevation maintained the bridge deck well above the 15-meter high water level reached by the wild river during the flood season.
The bridge is considered to be the longest bridge in the ancient world until this record was broken by Italian engineers constructed a longer span in 1377. The discovery of the bridge was published in Civil Engineering Magazine and in National Geographic Magazine. The History Channel produced a video with an account of this unique feat of Maya engineering.
Medium span bridge structuresMaya engineers constructed numerous bridges with spans up to 50 feet long with timber beams. This figure shows a cross section of the Classic Period Maya bridge over the Pusilha River.
Short span bridges
Maya short span bridges crossed streams, canals and moats in urban environments. Figure xx indicates a Maya bridge over the Otulum River at Palenque and the figure to the right shows the Maya bridge over the moat surrounding the city of Becan.