Short answers, pulled from the story.
Kos Minars are medieval Indian milestones, solid round pillars about 30 feet tall built on masonry platforms, erected at every kos along royal routes on the northern Indian subcontinent. They served as distance markers for travelers on roads including the Grand Trunk Road, and the Archaeological Survey of India has described them as an integral part of India's national communication system.
Kos Minars were introduced by Sher Shah Suri, the 16th-century Pashtun ruler of the Sur Empire, who erected improved brick pillars plastered with lime at every kos along royal routes. Later, Akbar issued an order in 1575 to extend the network, and Shah Jahan continued adding to it during the Mughal period.
A kos is one fourth of a yojana, an ancient Indian unit of distance representing approximately 3.22 km. A case study from Punjab documented a kos length of approximately 4.2 km, indicating some regional variation. Kos Minars were placed at every kos interval along major royal roads.
Only 110 Kos Minars survive from the Mughal-era network that once numbered around 600. The Archaeological Survey of India counted 49 in Haryana alone, with additional surviving examples in Punjab and other states.
The introduction of Imperial units by the British and, later, independent India's adoption of the International System of Units made the kos unit of measurement obsolete. Without a practical navigational role, the minars were gradually ignored and deteriorated.
Conservation work on Kos Minars in Jalandhar district started in 2016, with grill fencing erected at each minar to protect the original structures. Restoration work for nine Kos Minars near Mathura began in 2018, and the Archaeological Survey of India has given Kos Minars protected status, with courts ordering encroachments cleared.