The Lighthouse of Alexandria was a tall tower built in the third Century BC on the island of Pharos in Alexandria, Egypt, to serve as that port's landmark, and later, as its lighthouse. With an estimated height between 383 feet and 450 feet, it was among the tallest man-made structures on Earth for many centuries. It was the only wonder of the ancient world that had a practical use, in addition to its architectural elegance. For sailors, it ensured a safe return to the Great Harbour. For architects, it was the tallest building on Earth. And for scientists, it was the mysterious mirror that fascinated them the most.