Kabul, Afghanistan ? The new Kabul Serena hotel rises in the middle of the city, a palace of sandstone built around gardens that even in summer’s drought gleam green.

Step inside and you step out of Afghanistan.

The central air conditioning is a perfect temperature, the inlaid marble floors are a soothing cream and, miraculous for a city where open sewers crisscross neighborhoods and dust coats every surface, the place smells clean.

Afghans look at the new affluence with disbelief. The Serena’s prices are beyond their means, and there is no hint in its well-appointed reception rooms of the unseen enemies that haunt Kabul neighborhoods: a government worker kidnapped here; a grenade thrown into a shop selling western music there.

Still, Kabul has an openness and vibrancy it lacked four years ago. Nearly 2 million people have returned to Afghanistan, the majority to Kabul. Many city women eschew burkas, walking on the streets with just a white veil on their heads, their faces uncovered.

All this activity gives Kabul a busy feel, a confidence, the past mingling with the present, pushcarts and high-speed printers.

But unease haunts the capital, an apprehension, a mood similar to what I witnessed in Iraq a few months after the U.S.-led invasion, when the euphoria of the first weeks without Saddam Hussein evaporated in the desert air.

In July, a bomb targeted a busload of Afghan National Army soldiers barely 10 minutes from the Hotel Serena. No one died, but 35 were injured. In a city that hadn’t seen any bombings in more than a year, the attack was one of four blasts in two days.

As in Baghdad, there is rising resentment of the United States on the streets of Kabul.

Why has America let its aid organizations contract with corrupt companies who keep it for themselves? Why don’t they use more local labor? Why, in five years, are so many places, even in Kabul, still without electricity, still without drinkable water?

In May, the anger burst into the open after an American convoy careened into civilians, killing five people. A crowd rampaged through the streets, and the violence left nine people dead and more than 90 wounded. Rioters were shouting “Death to Karzai” and “Death to America.”