Qila Rohtas is a garrison fort and could hold a force of up to 30,000 men. Due to its location, massive walls, trap gates and 3 Baolis (stepped wells) it could withstand a major siege although it was never besieged.
Most of the fort was built with ashlar stones collected from its surrounding villages such as Tarraki village. Some parts of the fort were built with bricks.
The fort is irregular in shape and follows the contours of the hill it was constructed on. The fort is exactly 5.2 km in circumference. A 533 metre long wall divides the citadel (for the Chieftain) from other parts of the fort.
The fortification has 68 bastions (towers) at irregular intervals. Out of the 3 Baolis, one of them is in the citadel and the rest are in the other parts of the fort. One of the Gates (Langar Khani) opens into the citadel and is a trap gate because it is in the direct line of fire of the bastions.
The Khwas Khani gate is an example of double walling. A small enclave on the western side is a citadel within a citadel. It is accessible by only one gate and also had a very fine Baoli which suggests that it was meant for the Chief and his family. In this citadel there is a beautiful Mosque called the Shahi Mosque (Not to be confused with the one in Lahore). There are no palaces in the Fort except for a structure built by Raja Man Singh called the Haveli of Man Singh. It is built on the highest point of the citadel.
Cost of construction
The work on this fort was started in 1541 with Todar Mal Khatri, the revenue minister in charge of the project. The Gakhars whose area the fort was built on refused to provide labour for this project.
Todar Mal faced with such problems informed Sher Shah about these difficulties who wrote in reply,” I know you for a man of business, understanding and intelligence. I see no work can be expected from you, because you consider money as your friend. When I have commanded you to do a thing you ought not to have cared for money in fixing the rate. Whatever be the expenses, shall be borne by my government.”
After receiving this reply, he fixed one red ashrafi (gold coin) for each slab on the first day. The rate gradually decreased to one paoli (silver coin) and then to one bahluli (copper coin).
Because of the boycott the cost of construction was huge. It would have been much lower had it not been for the Ghakkars. The following sources all give slightly different estimates of the cost
“The amount is 16, 10, 00,000 dams and something more, which is 34, 25,000 Rupees of Hindustan, 120,000 Tumans of Iran or 1,21,75,000 Khanis of Turan”. According to Tarikh-i-Daudi, its cost is 80,505,002 Dams (Bahlulis).
Choa Sahib (Sikh Shrine outside the fort)..... The choa (the fountain discovered by Guru Nanak) lies outside the fort. Shershah Suri tried to cover it for the use of water by his military. He built the wall around it to take it inside. But every time he tried to cover, the choa miraclusly went outside the wall of the fort. He tried 7 time. Finally he gave up.(Reference??)