In a new three-part series historian Michael Scott explores deep underground using the latest laser-scanning technology and Virtual Reality to reveal the historical secrets of three great cities: Cairo, Athens and Istanbul. 　　The Invisible Cities scanning team helps us to see these cities as no human eye ever could; in Cairo Michael explores deep inside and beneath the first pyramid ever built at Saqqara and finds out how it helped inspire the Great Pyramid of Giza; in Athens he reveals the secrets of a temple on the Acropoli……