Ahvaz, Iran

Capital City

Living in one of the world's most polluted cities isn't for the faint-hearted. With temperatures regularly hitting 45°C (113°F) and occasionally surging past 50°C (122°F), Ahvaz's 1.18 million residents endure extreme desert conditions alongside heavy industrial pollution from the region's oil industry.

This gritty industrial hub straddles the Karun River in southwestern Iran, earning its nickname "City of Bridges" from the nine spans connecting its eastern and western districts. The administrative and industrial heart occupies the right bank, while residential areas cluster on the left. Its strategic location near the Iraqi border and Persian Gulf has shaped its development as a key transportation nexus, though this positioning proved costly during the Iran-Iraq War when the city suffered severe damage.

Once a small settlement of just 2,000 people in the 1800s, Ahvaz transformed after oil's discovery in the early 20th century. Today it's a multilingual metropolis where Persian, Arabic, Kurdish and various local dialects intermingle. The city's industrial backbone includes steel production at the Foolad facility, while its universities and status as provincial capital of Khuzestan cement its regional importance - despite the challenging environmental conditions that earned it WHO's dubious distinction as the globe's most air-polluted city in 2011.