After the collapse of the Old Kingdom, Egypt entered a turbulent phase, which is usually referred to as the First Intermediate Period. The reunification of the country, with the so-called Middle Kingdom, came with the kings of Thebes (today's Luxor) around 2 100 BC. As a consequence, Thebes became the most important city, and its main God Amun - united with Ra - became the most important God of Egypt, Amun-Ra. In the Middle Kingdom and even more, later, in the New Kingdom the religious structures and associated priesthood progressively acquired power, and so many temples were constructed and enlarged in the course of the centuries. The most important one is certainly the temple of Amun at Karnak. Many pharaohs made additions to Karnak, the most famous perhaps being the hypostyle room added by Ramesses II around 1 250 BC. The axis of the temple runs along the solstitial line midwinter sunrise/midsummer sunset. The front is towards the Nile and sunset. However, the western horizon is occupied by the Theban hills, so that the Sun sets before filtering along the axis. The horizon is instead flat to the south-east, and therefore the temple is definitively aligned to the winter solstice sunrise: the spectacle of the rising Sun penetrating the temple can still be enjoyed today. An inscription in the temple reads: “We applaud your beautiful face, you biggest of all Gods, Amun-Ra”. And indeed, we can understand why, at midwinter dawn once a year. But why was such an important temple oriented to the rising Sun at midwinter? Probably the reason is in the structure of the Egyptian calendar. In fact, the Egyptian calendar was made up of three seasons of 120 days each: akhet (Inundation), peret (Growth), shemu (Harvest), plus 5 added days for a total of 365 days, without any correction such as leap years. Of course, the Egyptians knew that their calendar was too short to take into account the length of the tropical year, which is a bit less of 365 days and 1/4. To fix ideas we shall ignore here this small difference; then, we can say that the Egyptian calendar drifts of one solar day each four years, making a complete turnaround in 4 x 365 = 1 460 years. The Egyptian calendar started with the summer solstice and the heliacal rising of Sirius around the half of the 27th century BC, so in the years around the foundation of Karnak, which occurred around the start of 20th century BC, it completed one half of this wandering. Therefore, New Year's Day coincided the winter solstice, and this occasion was celebrated in the project of Karnak temple. Another wonderful example of temple orientation related to the Sun and to the calendar is at Abu Simbel, where around 1 250 BC Ramses II built two temples excavated in the rock near the bank of the Nile (today they are reconstructed in an elevated position due to the formation of the artificial lake of the Assuan dam). The façade of the main temple houses four gigantic statues of the Pharaoh. The interior is organised along a series of halls aligned with one another and decorated with the heroic life of the king. The chapel at the end contains four seated statues representing gods: Ptah, Amun-Ra, Ramesses II - who of course considered himself as a living God - and Ra-Horakhti. On February 20 and October 22 of every year, and for a few days before and after, the Sun rises in alignment with the axis of the temple. The light rays pass along the axis and reach the chapel at the end of the building. The Sun carefully avoids Ptah - a chthonic God, related to the underworld - but illuminates Amun-Ra, then Ramesses II and, in the end, also Ra-Horakhti, the personification of the solar disk. This spectacular hierophany implies an architectural constraint that conditioned the entire planning of the Abu Simbel main temple right from the onset. Again, as in Karnak, the origin is calendrical. These two dates in fact marked the beginning of the two seasons Shemu and Peret at the time, around 2 700 BC, when the Egyptian calendar was devised. When Ramesses II accessed to the throne, 1 460 years were elapsed, so that he could celebrate himself as the king under which the calendar re-aligned with the solar year.
