The imposing ruins of Shahr-e Zohak guard the entrance to the Bamiyan valley, perched high on the cliffs at the confluence of the Bamiyan and Kalu rivers. Built by the Ghorids, they stand on foundations dating back to the 6th century. Genghis Khan's grandson was killed here, bringing down his murderous fury on the whole Bamiyan valley as a result. The colloquial name Zohak is taken from the legendary serpent-haired king of Persian literature.

The towers of the citadel are some of the most dramatic in Afghanistan. Made of mud-brick on stone foundations, they wrap around the side of the cliff, with geometric patterns built into their crenellations for decoration. The towers had no doors, but were accessed by ladders that the defenders pulled up behind them.

Passing the towers, a path leads up through a rock tunnel and the main gateway of the fortress, before switching back up the hill, past ruined barracks and storerooms. Take extreme care here - the route is marked with red rocks for landmines (many of then faded or peeling), so don't stray from the well-worn path. The path quickly steepens and becomes increasingly exposed to strong crosswinds. A rusting anti-aircraft gun and abandoned soldier's post market the summit.

The views over the confluence of the two rivers are awesome, with their thin strips of cultivated green providing a stark contrast to the dry pink and tan of the mountains. The location's strategic value is immediately apparent, and the heights seemingly impregnable to all except Genghis.

Shahr-e Zohak is around 9km from Bamiyan. To get there take any westbound transport out of Bamiyan. As the confluence of the Bamiyan and Kalu rivers is where the roads from the Shibar and Hajigak Passes meet, any transport should be able to drop you there. Ask to be let out at Tupchi village (Afg40, 25 minutes) or the checkpoint at Shashpul half a kilometre after it, which is next to the confluence. The soldiers here will check you have a ticket from the Director of Information and Culture in Bamiyan. From here, walk about 1km following the Kalu, until you can see a simple wood-and -earth bridge, roughly level with the last of the citadel's towers (if your vehicle is going in the Hajigak Pass direction - the nearest villages to ask for are Dahane Khushkak, Paymuri or Sawzaw - you can be dropped at this point). A short walk along the edge of a field brings you to a pass leading up to the towers.

Hiring a vehicle from Bamiyan will cost around 1100Afg return, according to your haggling skills.