Great Pyramid of Khufu

For 3,800 years this was the tallest structure on earth. Inside, an ascending corridor leads to the Grand Gallery — a corbelled passage 47 metres long and 8.6 metres high, built with a precision that still has no full explanation — and on into the King's Chamber, a granite room holding an empty, lidless sarcophagus that was placed during construction because it is too large to pass through the doorway.

Entry is by a separate ticket with a daily cap. The climb is steep, hot and requires bending double in places; it is not suitable for anyone with claustrophobia or knee problems.

Completed around 2560 BC for Khufu, second pharaoh of the Fourth Dynasty. The base is level to within 2.1 centimetres across 230 metres and the sides are aligned to true north within a twentieth of a degree.