Crypto lighthouses: The Lighthouse of Alexandria

The Lighthouse of Alexandria also called Pharos of Alexandria, is one of the Seven Wonders of the World and the most famous lighthouse in antiquity. It was a technological triumph and is the archetype of all lighthouses since. It was finished during the reign of Soter’s son Ptolemy II of Egypt in about 280 BCE. The lighthouse stood on the island of Pharos in the harbor of Alexandria and is said to have been more than 350 feet (110 meters) high; the only taller man-made structures at the time would have been the pyramids of Giza. According to the ancient sources, the lighthouse was built in three stages, all sloping slightly inward; the lowest was square, the next octagonal, and the top cylindrical. A broad spiral ramp led to the top, where a fire burned at night.