of the credibility of archaeoastronomical sites, Cotte and Ruggles gave Newgrange as an example of a Generally accepted site, the highest of their four levels of credibility. Clive Ruggles notes: Egypt Since the first modern measurements of the precise cardinal orientations of the pyramids by Flinders Petrie, various astronomical methods have been proposed for the original establishment of these orientations. It was recently proposed that this was done by observing the positions of two stars in the Plough / Big Dipper which was known to Egyptians as the thigh. It is thought that a vertical alignment between these two stars checked with a plumb bob was used to ascertain where north lay. The deviations from true north using this model reflect the accepted dates of construction. Some have argued that the pyramids were laid out as a map of the three stars in the belt of Orion, although this theory has been criticized by reputable astronomers. The site was instead probably governed by a spectacular hierophany which occurs at the summer solstice, when the Sun, viewed from the Sphinx terrace, forms—together with the two giant pyramids—the symbol Akhet, which was also the name of the Great Pyramid. Further, the south east corners of all the three pyramids align towards the temple of Heliopolis, as first discovered by the Egyptologist Mark Lehner. The astronomical ceiling of the tomb of Senenmut (BC) contains the Celestial Diagram depicting circumpolar constellations in the form of discs. Each disc is divided into 24 sections suggesting a 24-hour time period. Constellations are portrayed as sacred deities of Egypt. The observation of lunar cycles is also evident. El Castillo El Castillo, also known as Kukulcán's Pyramid, is a Mesoamerican step-pyramid built in the centre of Mayan center of Chichen Itza in Mexico. Several architectural features have suggested astronomical elements. Each of the stairways built into the sides of the pyramid has 91 steps. Along with the extra one for the platform at the top, this totals 365 steps, which is possibly one for each day of the year (365.25) or the number of lunar orbits in 10,000 rotations (365.01). A visually striking effect is seen every March and September as an unusual shadow occurs around the equinoxes. Light and shadow phenomena have been proposed to explain a possible architectural hierophany involving the sun at Chichén Itzá in a Maya Toltec structure dating to about 1000 CE. A