<P> The Maya were keen observers of the sun, stars, and planets . E-Groups were a particular arrangement of temples that were relatively common in the Maya region; they take their names from Group E at Uaxactun . They consisted of three small structures facing a fourth structure, and were used to mark the solstices and equinoxes . The earliest examples date to the Preclassic period . The Lost World complex at Tikal started out as an E-Group built towards the end of the Middle Preclassic . Due to its nature, the basic layout of an E-Group was constant . A structure was built on the west side of a plaza; it was usually a radial pyramid with stairways facing the cardinal directions . It faced east across the plaza to three small temples on the far side . From the west pyramid, the sun was seen to rise over these temples on the solstices and equinoxes . E-Groups were raised across the central and southern Maya area for over a millennium; not all were properly aligned as observatories, and their function may have been symbolic . </P> <P> As well as E-Groups, the Maya built other structures dedicated to observing the movements of celestial bodies . Many Maya buildings were aligned with astronomical bodies, including the planet Venus, and various constellations . The Caracol structure at Chichen Itza was a circular multi-level edifice, with a conical superstructure . It has slit windows that marked the movements of Venus . At Copán, a pair of stelae were raised to mark the position of the setting sun at the equinoxes . </P> <P> Triadic pyramids first appeared in the Preclassic . They consisted of a dominant structure flanked by two smaller inward - facing buildings, all mounted upon a single basal platform . The largest known triadic pyramid was built at El Mirador in the Petén Basin; it covers an area six times as large as that covered by Temple IV, the largest pyramid at Tikal . The three superstructures all have stairways leading up from the central plaza on top of the basal platform . No securely established forerunners of Triadic Groups are known, but they may have developed from the eastern range building of E-Group complexes . The triadic form was the predominant architectural form in the Petén region during the Late Preclassic . Examples of triadic pyramids are known from as many as 88 archaeological sites . At Nakbe, there are at least a dozen examples of triadic complexes and the four largest structures in the city are triadic in nature . At El Mirador there are probably as many as 36 triadic structures . Examples of the triadic form are even known from Dzibilchaltun in the far north of the Yucatán Peninsula, and Q'umarkaj in the Highlands of Guatemala . The triadic pyramid remained a popular architectural form for centuries after the first examples were built; it continued in use into the Classic Period, with later examples being found at Uaxactun, Caracol, Seibal, Nakum, Tikal and Palenque . The Q'umarkaj example is the only one that has been dated to the Postclassic Period . The triple - temple form of the triadic pyramid appears to be related to Maya mythology . </P> <P> The ballcourt is a distinctive pan-Mesoamerican form of architecture . Although the majority of Maya ballcourts date to the Classic period, the earliest examples appeared around 1000 BC in northwestern Yucatán, during the Middle Preclassic . By the time of Spanish contact, ballcourts were only in use in the Guatemalan Highlands, at cities such as Q'umarkaj and Iximche . Throughout Maya history, ballcourts maintained a characteristic form consisting of an ɪ shape, with a central playing area terminating in two transverse end zones . The central playing area usually measures between 20 and 30 metres (66 and 98 ft) long, and is flanked by two lateral structures that stood up to 3 or 4 metres (9.8 or 13.1 ft) high . The lateral platforms often supported structures that may have held privileged spectators . The Great Ballcourt at Chichen Itza is the largest in Mesoamerica, measuring 83 metres (272 ft) long by 30 metres (98 ft) wide, with walls standing 8.2 metres (27 ft) high . </P>

When did the mayan empire start and finish