There is a mountain in the middle of Kabul. Forty or 50 years ago, when Kabul was a small town of 250,000, it wasn’t a problem. Now that Kabul has grown to about 4 million, it’s a pain in the city’s neck.

Kabul is surrounded by mountains. It sits in a bowl. There are limited areas for growth, and they’re just about used up.

They extend to the other side of the mountain, which means that to get from one side of the city to another, there is a bottleneck. Only a couple of roads — and really only one main one — go around the mountain. It increases the travel time during morning and evening rush hours by at least a half-hour, not only because of the traffic but simply because of the distance. Even between peak periods of traffic the delay is noticeable.

If one could go over the mountain, the time would be much shorter. But the only roads that go over the mountain are narrow, twisting, rutted dirt roads, and top speed is 25 miles an hour at any good stretch. Mostly, it’s 10 miles an hour or slower, and a dead stop when two cars meet and try to negotiate their way past each other. Because on this mountain there are thousands of homes squeezing in on the roads.

Land on Kabul flats, if you will, has run out. High-rise apartments are going up, and the old mud brick buildings are coming down to make room. Most Afghans can’t afford these new apartments. A friend of mine who knows Kabul well says war lords, drug dealers and some of the slowly growing middle class, mostly merchants, live in the high rises. Kabulis who drive taxis, run fruit or vegetable stands, bake bread, or do menial government work — in other words, the vast majority — lived in the mud brick houses and now are being displaced. So they’ve moved up the mountain, onto land that was pretty much free, and built their new homes.

These are mean homes, not fancy, although a few people have chosen to put up more expensive residences that stand out like a rose against a gray sky.

Children dart in and out of the mountain homes and run along the roads on errands or at play. Old men sit on the doorsteps and look out over the city below and the mountains beyond. Cars dented from unfortunate contact with other cars on Kabul’s crowded streets, dirty from the constant dust in the air, and weary of laboring up and down the steep mountain every day, ease their way around hairpin turns, avoiding the kids, the old men and the veiled women who are out to find food to cook for dinner.

The roads, of course, are not planned. They are almost an accident, more of a trail that goes wherever there isn’t a house. Some of these houses have no glass in the windows. At night, they are shuttered. They sit on bare rock; there is almost no vegetation here. The children play among the mountain scree and withered scrub bushes. They laugh and chase each other and hold the hands of their smaller siblings. They are kids, just like everywhere. But then they are called to carry water or help with something at home, and they scamper through the open doorways.

Somehow electricity has come to the homes on the mountain. It seems almost a mystery — it should be nearly impossible to bore a hole in this ground to hold a pole strung with wires. But at night, the mountain is ablaze with lights from the windows of the houses. They didn’t used to be.

Two other utilities we take for granted here have not made the climb up the side of the mountain: water and sewage.

Water is carried up from below, in those dusty, dented cars or on the donkey drays that are a common sight. Not a good solution, but the only one available.

But the sewage? That’s the problem with no solution. There are outhouses, of course, and as environmentally devastating as those are, there is something worse. Rain.

When it rains on the mountain, the sewage from the outhouses is washed out. There is no soft ground, no vegetation to soak up the water. It flows into the shallow roadside ditches that are everywhere, on the mountain and in the city. The sewage from those thousands of homes fills the ditches to the top and over.

Those living in the topmost houses are spared what happens below. The sewage flows down the ditches, down the side of the mountain, picking up more sewage from the lower homes, surging downward and into the city — into the areas closest to the mountain, into the ditches in areas farther away, into the lives of the people who live where there is some form of sanitation system.

Raw sewage from thousands of homes on the mountain. Homes that are there because the people who live in them have been displaced, or because Kabul as a city could never handle the millions who have moved there looking to escape violence or to find work.

Down below in the city, men and boys clear the muck out of the sewers. In the rainy season it’s an everyday job. I don’t know what they do with it. But they have to clean it out because otherwise cholera would threaten a million or more people, just as polio still continues to threaten them today. Raw sewage is a prime carrier of the polio virus.

The mountain is an inconvenience every day for drivers trying to get from one side of town to the other. It’s a homeland for many who can’t afford to live in the city. It’s a hazard to those who live below it. It’s a health threat whenever it rains.

There is a mountain in the middle of Kabul. At night, it glimmers peacefully, beautifully, like stars on a romantic evening. It’s anything but romantic. It is its own hell in the sky.