Manila, the capital city of the Philippines, has liabilities lined up like dominoes.

Not only is the city the densest in the world — at 46,000 people per square mile, twice the density of New York City — but it's located on the Ring of Fire, a series of volcanoes in the Pacific Ocean that inundates Manila with earthquakes and typhoons.

On top of the environmental concerns are economic and demographic ones. Manila's fertility rate is a soaring 3.1 children per woman, and residents face rampant disparity in living conditions. High-rises are going up, as are makeshift communities to house those who've been displaced by natural disaster or financial ruin.

Here's what life is like in the most crowded city in the world.