Axum

Capital of the Aksumite Empire, a major naval and trading power that controlled Red Sea commerce from the 1st to 8th centuries AD. The site contains exquisitely carved monolithic stelae from the 3rd-4th centuries, with the largest fallen stela measuring 33 m -- possibly the biggest monolith ever attempted to be erected. Christianity was adopted in the 4th century, and the Church of St. Mary of Zion is said to house the Ark of the Covenant. Inscribed as a UNESCO World Heritage Site in 1980.