Large framed portraits of prominent Mumbai citizens hang from the upper level of the Corporation Hall. This is Keshav Sitaram Thackeray (1885–1973), father of Balasaheb Thackeray, founder of the political party Shiv Sena. K.S. Thackeray was an author and social activist. He was also one of the key leaders of the Samyukta Maharashtra Samiti that campaigned for the creation of Maharashtra state based on linguistics and for the inclusion of Mumbai as the capital of Maharashtra.
Marble statue of Mahatma Gandhi inside the Corporation Hall. Hanging from the ceiling are microphones marked with numbers for respective speakers, one of the many additions made to suit changing technology. The original stained-glass panels from the bay window have been replaced with metal plaques commemorating Mumbai's history and prominent landmarks.
On the second level inside the BMC building, stained-glass windows illuminate a museum that traces the evolution and history of the Municipal Corporation and the stellar role of Frederick W. Stevens in the design of the building. This museum also has a collection of old maps of the Greater Mumbai Region and old photographs of Mumbai.
Frederick Stevens raised the height of BMC to 235 feet. At the rear of the tower, he made provision for a lift shaft, making it the first building in Mumbai to use a hydraulic lift. The water which was used in running the lift was stored between the outer and inner domes of the tower. The tanks had a capacity of 40,000 liters.
Another architectural feature common between the BMC building and CSMT is the extensive use of stained-glass windows. They depict various themes linked to the evolution of Mumbai under the British Empire, for example, in this window, the wooden ship is symbolic of the maritime trade that brought wealth and colonial administration to the city.
Frederick W. Stevens died in 1900. During his professional career as an architect, Stevens was exceptionally prolific. Many iconic buildings in Bombay are his masterpieces. This includes, in addition to the CSMT and the BMC building, the Royal Alfred Sailor's Home (Maharashtra Police Headquarters), the Bombay, Baroda & Central India Railway Offices (Western Railway Headquarter), the Chartered Bank building, the Mulji Jetha Fountain and the Army and Navy Cooperative Society Store.
Though externally the BMC building has largely retained Frederick Steven's original design, the interiors have periodically been modified to cater to political and nationalistic compulsions after the end of British rule. Here, for example, portraits of Mahatma Jyotirao Phule, Chhatrapati Shivaji Maharaj, and Dr. B.R. Ambedkar have been added over doorways.
Over 128 years, the BMC building has been modified to make provisions for piped water, electrical fittings and other modern amenities. The usage of spaces has also changed as the municipality has expanded its way of functioning. For example, rooms on the ground floor have been converted to offices of political parties who send elected corporators to BMC.
Frederick Stevens’ design of large windows allowed plenty of natural light and a breeze to pass through, keeping the buildings ventilated and illuminated. This was a practical necessity because, at the time of its construction, buildings didn't have electricity. The BMC building was, in fact, the first building in Mumbai to be fully electrified before its inauguration.
The inner dome is located at a height of 90 feet from the ground. In recent times, the inner dome has been beautifully restored as part of ongoing conservation efforts. Other than structural restoration, the dome has been painted and special lighting has been installed for daytime illumination.