Some 16km northwest of Jhelum, colossal Rohtas Fort is an extraordinary example of military architecture. It was started in 1543 by the Pashtun ruler Sher Shah Suri, to protect the strategic Peshawar to Calcutta (now Kolkata) road from the Mughals and their allies. He never lived to see its completion and work was carried on by succeeding rulers. However, it was soon made redundant when Akbar moved his frontier to Attock and built a new fort there.
The vast fort is now in ruins except for the crenulated outer walls and most of its 12 gates and 68 bastions. The best-preserved remains are to the west; walk through the town to the western Sohal Gate to start your explorations. Built to an irregular plan on hilly ground, its 12m-thick terraced ramparts have a perimeter of more than 4km and vary in height from 10m to 18m. You can still walk along some of them but they are crumbling, so watch your step. An internal wall separates the inner fort (or citadel for the elite) at the northwest from the outer fort of soldiers and citizens, where the sleepy town still exists.
Little remains of the interior, but there are two pavilions of the haveli of Man Singh (governor of Lahore and a general in the time of his son-in-law Akbar the Great), which you can climb for a view over the whole fort. To the west, at the pinnacle of the outer wall, a high stone platform marks the burj (execution tower); victims would be thrown from here into the ditch below. Two gates in the northern wall lead down to freshwater wells and the Kahan River. You could spend two or three hours exploring the grounds. Bring a hat, and although drinks can be bought in the town, it's wise to carry your own.