Like the walls of a giant fortress, the snow-covered peaks of the Spin Ghar, or White Mountains, rise from the haze as you drive south from Jalalabad.
Opium remains far more lucrative than many other crops
It is a spectacular landscape, but one swirling in rumour and tension these days.
Buttressing these peaks are the wooded hills of Tora Bora, famous now as the last known hiding place of Osama Bin Laden.
But today it is the setting for another battle, one arguably far more important to Afghanistan's future.
This is one of the main areas for growing opium poppy - source for most of the world's heroin.
With a recent UN report showing a two-thirds rise in poppy cultivation this year, Afghan and international efforts to curb the illegal trade are intensifying.
Yet there are signs such efforts could already be failing.
Nader Khan says his crops and goats were affected by spraying
In the villages abutting Tora Bora's slopes, people are angry.
They believe unidentified aircraft have been secretly spraying herbicide on their opium fields, which they say they depend on for survival.
Most people here point the finger at the Americans or the British, the lead players in international efforts to combat the Afghan drugs trade.
"I heard the planes late at night about 10 days ago, circling above," says farmer Nader Khan, who lives in Pachir wa Agam district.
In the morning, he described seeing tiny grey pellets spread across his fields.
"I had planted just a small piece of land with poppy," he insists, showing me the size of the plants, no more than 10cm high.
"But now all the plants are finished. Some of my other crops were killed too."
Giving me a tour of his land, he points out a patch of wilting and yellowing onions, although there was no way of telling if this was because of the alleged spraying.
Nader Khan says his goats were also affected, although he won't say how. And when a crowd of fellow villagers gathers to listen, there is more than a little theatre in his answers and gestures.
In Kabul, the American embassy insists the US government has "not conducted any aerial eradication, nor has it contracted or sub-contracted anyone to do it on its behalf". The British embassy has given similar denials.
And some experts question why anyone would try to spray so early on, when the opium plants are so young.
Nevertheless, the mystery of what happened over the Tora Bora opium fields in the weeks after Ramadan will not go away.
Descriptions of tiny grey pellets match a sample that has been given to the BBC by a farmer from the neighbouring district of Khogyani.
Afghan authorities, who have expressed concern to the British government over the allegations, say they are testing substances collected immediately after reports of the spraying emerged. No results have been released so far.
Whatever the explanation, it has had the affect of spreading mistrust of any attempts by outsiders - Afghan or foreign - to stop poppy growing.
"Why do they do this secret spraying?" demands another farmer. "If they help us, with new roads, dams and electricity, then we won't grow it."
That may be the explanation, argue some Western anti-narcotics officials in Kabul - a deliberate attempt by some major players in the Afghan drugs trade, aimed at stirring opposition to other "real" eradication efforts planned for the next few months.
If there really was a plan to kill off poppy plants early in the season, it does not appear to be working. In Pachir wa Agam, affected plots have already been re-ploughed.
Several fields can be seen from which the tiny leaves of new opium plants are sprouting - fields the farmers said had been sown with wheat.
Nothing is ever as it seems in Afghanistan.
The reality is that opium is embedded in the economy here.
"I have been growing poppy since Zahir Shah's time," says Haji Zarghoun, referring to Afghanistan's former king, who ruled until 1973.
The economics are simple. Haji Zarghoun says he earned around 300,000 Afghanis - about $6,600 - last year from selling the opium resin from his poppies.
That is at the higher end of the income spectrum for an opium farmer. But compare that to the average wage in Afghanistan of around $200 a year.
"I have 30 people in my family, how can I feed them if I don't grow opium?'" he asks, then begins to cry.
"We know it is against Islam, but we have no choice. If you're hungry you can eat pork."
In fact, some international assistance is being organised for opium farmers in this region.
This weekend, the American development agency USAID is due to announce the distribution of 500 tonnes of wheat seed for Nangahar province, of which Tora Bora is a part.
Opium is destroyed near Kabul. Some experts say tackle gangs first
But even those who will be administering the programme, like provincial governor Haji Din Mohammed, are sceptical about its benefits.
"It is almost the end of the wheat planting season," he says.
What is more, wheat does not grow as well in the highlands around the Spin Ghar. Nor, more importantly, does it bring in anywhere near as much cash as opium.
Patrick Fine, Afghanistan director for USAID, says it knows this is not the answer to the problem. The wheat distribution is "just the first step in a much bigger programme" aimed at promoting alternative sources of income.
Later this year, Mr Fine says the US will be funding a major jobs programme, paying people in Nangahar and the two other main drug producing provinces to repair irrigation channels, road and other infrastructure work.
There is concern among development experts in Nangahar that the US is putting too much emphasis on eradicating poppy crops.
"It will not do what people think it will do," says Leo Brandenberg, team leader in Jalalabad for the German aid agency GTZ.
GTZ is running a development programme in the province to reduce its reliance on opium.
Mr Brandenberg's experience in Thailand showed it was better to leave farmers alone and concentrate more on breaking up drug gangs and trafficking networks first.
Governor Din Mohammed is worried too.
With so much pressure from the US to see poppy fields destroyed, he says there could be violence in Nangahar.
"There will be no choice for the people," he warns.
"It would be better to do this eradication and help at the same time."