After that you have visited the tomb of Pari bibi, the next is you will see in the complex is the hammamkhana. Standing a distance of 130 feet from the western bank of the tank, it is a graceful double-storied building with a projected domical annex to its west. This is reputed to be the residence, audience hall and hammam belonging to Nawab Shaista Khan.
The hammamkhana follows the same construction process as the tomb. The ground floor of this elegant building consists of a central hall, measuring 26’-7”x18’-3”, flanked on either side by a square apartment. It has three arched entrances on east was provided with an ornamental oblong flank in the middle with a fountain in it. Across the fountain on western massive wall an arched entrance, opening under a half-dome gives access to the main hammam and toilet complex flagged with glassy hexagonal tiles and provided with water heating systems and changing rooms.
A narrow passage between the two half domes on either sides, leads to a cruciform large hall with rectangular alcoves on four cardinal sides (about 10’-5”x12-3”), forming four arms, each covered with a half dome which are relieved on the soffit with beautiful geometric fret work in plaster. Similar works could be seen in the ventilating aperture of domed roof of the central hall.
Along with the main cruciform hall four small rooms (9’-5”x9’-0” and 10’-5”x12’-3”) have been added between the arms of the cross, of which the top left being a changing room; top right a heating room with an oven in the middle, to the bottom left, a toilet and to the bottom right, a tank with steps for a dip in warm water, having inlet and outlet of copper pipes for the regulation of water supply. Complicated scheme of earthenware pipes, embedded into the thickness of walls of these chambers were fixed to supply hot and cold water to the hammam.
The floors of all these apartments were similarly flagged with brilliant encaustic tiles and provided with ingenious covered drains which carried the combined spoil-water into an elaborate vaulted drain on west of the whole complex. The waste water disposal pipes of the hammam were discovered in recent excavation emerging from its western end running westward possibly debauched through underground drain to an interesting elaborate masonry sewer with regularly spaced inspection pits on the western periphery of the fort.
All the chambers of the hammam are roofed over with squat domes with aperture at the apex which originally might have been fitted with glass cap for admitting light. To the south-west of the complex there were two more chambers (now destroyed), similar to the one between the boiler room and back of the audience hall on north-west. What is left now is a detached domed chamber, originally forming part of the complex, which is believed to be a boiler room or kitchen with a furnace in it.
At the center of the cruciform hall there is a slightly raised square platform with 8 feet sides, tastefully decorated with glazed tiles of multicolor, surrounded by a drainage channel around it. This seems to be the hypocaust platform on which one could enjoy a steam bath before dipping into the water of the tank. The central hypocaust platform is supported on four hollow brick columns at the four corners through which hot steam vapor rose upward for heating the central chamber. Recent excavation and clearance work to the north-western corner revealed arched entrances to the subterranean vaulted sub-structure with criss-cross passage carrying the hammam above on brick pillars.
Researches show that hammam complex as an adjunct to an Audience hall or reception hall like the one at the Lalbagh fort has similarities with the famous royal hammams near Amman, such as the Hammam-as-Sarrakh and at the Qusayr Amra built as annex to the audience hall in early 8th century. They both had three vaulted chambers for dressing, steam-bath in hypocaust system and toilet attached to a rectangular Audience hall with an alcove.
The upper floor of the Audience hall of the Lalbagh fort, reduced by 20 feet on either side, consists of a similar central hall along with two square chambers flanking it. The attractive architectural feature of the central hall is its east and west walls which are pierced by three multi-cusped arched wide openings each. These arched openings, which originally might have been fitted with delicate stone trellis, are supported on four ornamental stone columns on each wall.
In addition, the hall is spanned by a graceful curvilinear roof, simulating a typical Thatched do-chala hut of rural Bangladesh. It is a blending of indigenous elements, (practiced during the Sultanate period), with the imperial Mughal building style, a style which reversely travelled as far afield as Delhi and Lahore during the same period.
At present the building has been restored to its original condition by removing later accretions as far as possible and converted into a fort Museum of the same period. The museum displays on the ground floor a collection of arms and armor including bow and arrow, various types of daggers, spears, swords, shields, helmets, gauntlets, 3 types of pistols and guns: percussion lock, flint-lock and match-lock, while on the upper floor lies different varieties of Muslim calligraphy, replica of Mughal coins with a map showing the distribution on mint towns of India, ceramics including Chinese Jars, Persian porcelain, plates, celadon specimens of Mughal miniature painting including one of Prince Muhammad Azam, Asaf Jab, Mughal farmans and stone inscriptions.