A kos minar is a solid brick tower, around eight metres high, built at intervals of one kos, roughly three kilometres, along the imperial roads to mark distance.
They were built under Sher Shah Suri and extended under the Mughals, particularly Jahangir, and they run from Agra and Delhi toward Lahore and toward Ajmer.
A number survive in Punjab and Haryana, standing in fields beside a road that has moved, and they are the most numerous surviving Mughal structures in the region.
They are protected monuments in principle. In practice they stand unfenced in cultivated land, some are used as shrines, some have been encroached, and several are known to have been demolished.
They are also the most useful surviving evidence for the exact alignment of the Mughal road, because they were built on it and have not moved.
Nobody has surveyed and mapped the Punjab kos minars. Doing so would fix the sixteenth-century Grand Trunk Road on the ground to within a few metres.
The kos is not one distance. Akbar's kos was fixed at five thousand gaz, a Sher Shahi kos is not the same, and a local kos is different again, so the spacing measured between surviving towers on the Delhi to Lahore line does not come out uniform. The towers are the evidence and the arithmetic has to follow them.
There is no inscription on any of them. Nothing on a kos minar says who built it or when, which is why the dating rests on the road they stand along rather than on the towers themselves. Some have a small chamber or niche at the base and most are entirely solid brick.
A tower with no door, no writing and no use looks like nothing in particular at seventy kilometres an hour, which is most of why they go. A farmer levelling a field has no reason to keep one and nothing at the site tells him he must.