4. Petra, Jordan
Petra is a city erected with carved walls on a rocky cliff in Jordan. The word Petra comes from the Greek meaning Stone. Petra is the capital of the Nabatean kingdom built by King Aretas IV in 9 BC to 40 AD. The site was discovered by a Swiss swordsman named Johann Ludwig Burckhardt in 1812. The Jordanian Petra was designated a World Heritage by UNESCO on December 6, 1985. The Jordanian Petra is a symbol of Engineering and Protection.