The Mosul Dam was always meant to be a symbol of Iraq's grandiose ambition to escape poverty and underdevelopment.

But from the start, the $1.5 billion barrier north of the city was beset with significant engineering problems, now made worse after it became the center of a battle between Islamist insurgents and U.S. and Iraqi forces.

Despite its structural faults, the country's biggest dam, at 3.6 km long, built by a German-Italian consortium in the 1980s, is a vital water and power source for Mosul, Iraq's largest northern city of 1.7 million residents.