Karaj is where Tehran's sprawl runs out of road and the mountains begin, a city of well over a million people on the southern slopes of the Alborz. It is the capital of Alborz province, a commuter and industrial city with wide boulevards, apartment blocks and a long list of traffic jams, and for a rider heading north it is mostly a place to get through rather than linger in. Do the necessary things here, fill the tank, eat, check the bike, and then point the front wheel at the hills.
The reason for coming is the road. The route north from Karaj towards Chalus, known simply as the Chalus Road, is one of the great mountain highways of Iran, built in the 1930s to link the capital to the Caspian shore, and it climbs through the Alborz in a succession of bends, tunnels and gorges. Within a few kilometres of leaving the city, the landscape changes completely. You pass the Amir Kabir dam and its long reservoir, where the water is a surprising turquoise against the bare hills, and the road starts to coil upward past villages, orchards and roadside stalls selling local fruit and honey.
Traffic is the main hazard. On weekends and holidays the Chalus Road fills with cars from Tehran heading for the Caspian, and the queues can be long and the driving aggressive. Weekdays and early mornings are much calmer. The road itself is generally well surfaced and busy with trucks, so patience is as useful as skill, and care on blind corners and in tunnels is essential. Authorities sometimes manage the flow, and it pays to ask locally about conditions.
Fuel is no problem in Karaj, where stations are frequent, and the same is true of food. There are bakeries, kebab restaurants and tea houses along the main roads, and the traditional dish of the area, a simple grilled meat with rice and flatbread, is as satisfying here as anywhere. Bring cash and check the current rules on fuel purchase for foreign vehicles, which have changed over the years.
Karaj's own history is a little overshadowed by the capital next door, but it grew rapidly in the twentieth century as Tehran expanded. The best time to ride out is spring or autumn, when the hills are clear and the air is clean, and an early start gets you past the worst of the traffic.