Tughlaqabad
A fortress-capital finished in four years and abandoned in five, on a rocky spur in the south-east.
Ghiyas-ud-din Tughlaq built the third city as a soldier would: sloping rubble walls up to fifteen metres thick, more than a dozen gates, a citadel and a planned grid, all raised in about four years. It was the most heavily defended thing anyone had built in Delhi, and it is the least altered, because nobody came after to build on top of it.
The abandonment came almost immediately. Water was short, the succession was murderous, and the capital moved on within a few years of the founder's death. Tradition blames a quarrel with the saint Nizamuddin Auliya over labourers, and the curse he is said to have laid on the place — that it would stand empty or be lived in by herdsmen. It is now the emptiest large ruin in the city, thorn scrub and peacocks inside six kilometres of wall.
Almost the whole circuit of ramparts, the citadel, underground chambers, and the founder's tomb across the road.