This magnificent 14th-century ruin, half reclaimed by jungle and gradually being encroached on by villages, was Delhi's third incarnation, built by Ghiyas-ud-din Tughlaq. The sultan poached workers from the Sufi saint Nizam-ud-din, who issued a curse that shepherds would inhabit the fort. However, it's monkeys rather than shepherds that have taken over. There are fantastic emerald-green views. Interlinking underground rooms were used as storehouses. To reach the fort, take an autorickshaw from the Tughlakabad metro (one way/return ₹80/160).
The sultan’s well-maintained sandstone mausoleum once stood in the middle of a lake, but now is separated from his fallen city by a road. It's included in the entry ticket.
The ruins of the fort are fairly deserted, so it's best to visit them in a group or via walking tour. Be wary of the monkeys, who are prone to stealing belongings.