Its origins are an archaeological riddle worthy of Indiana Jones, but it's also a beacon of an oil-rich future. Welcome to the at least 7,000-year-old Arbil citadel in Iraq's northern Kurdistan region, a stunning walled fortress on a roughly 10-hectare site that some experts say is the oldest continuously inhabited settlement on earth (it's still occupied today, by a single family of 12). After years of stop-start negotiations, the citadel is finally set for a face-lift and likely World Heritage status.

Nobody knows who first built the towering castle-city, but it was already famous when Alexander the Great added it to his empire in 331 B.C. Some 1,500 years later, it took an invading Mongol army two tries and a six-month siege to storm it.

The list of successive ruling cultures is a history lesson in itself — Sumerian, Babylonian, Assyrian, Sassanian and Ottoman, among many others — and each left its history behind, adding to an archaeological layer cake now 32 m high.

Despite pleas from scientists going back to the 1930s, the citadel has never been fully excavated. This is all about to change. The renovation of the ancient hilltop city has become the keystone in an ongoing campaign to turn vast archaeological treasures into tourist dollars for Kurdistan, a stable and prospering region that bills itself as "the other Iraq."...