Arun Kumar, who heads a Mumbai charity, works with his team in some of the poorest neighborhoods in the city, helping residents lobby officials for civic amenities such as water, toilets, and public health centers.
This can take 10 to 15 years.
But even after 25 years Mr. Kumar's team has been unable to exit one area in the city's northeast: M-East Ward, where nearly three-quarters of the more than 600,000 residents live in slums close to the city's biggest landfill.
They are mostly Muslim, city data shows. Besides lacking civic amenities, the area also lags in social indicators such as life expectancy and infant mortality.
"Is it a lack of development or a deliberate denial of development to a certain section of the population?" said Kumar of the charity Apnalaya, which works with slum residents.
"The ward gets the same allocation in the city's budget as every other ward, but very little money is actually spent. There's apathy, and a lack of political will to do anything."
M-East Ward is just one example of how, as gleaming office towers, luxury apartments, and multi-storied malls mushroom in Indian cities, millions of poor Muslims, migrants and lower-caste Dalits are increasingly confined to squalid slums because of their religion or caste, analysts said.
"Our cities were always quite unequal because of wealth, and divisions on the lines of caste and ethnicity. Now, caste and religion are even bigger markers, ghettoization has increased and the segmentation looks set to get worse," said Anasua Chatterjee, a researcher at the Delhi University
"The (city) government is complicit in the reorganization of urban space along the lines of religion, resulting in closed and restricted neighborhoods for Muslims," said Ms. Chatterjee, who has written a book on Muslim neighborhoods in Kolkata city.
A Mumbai city official denied there was segregation or a deliberate denial of amenities in M-East Ward.
"We have budgeted for water, drainage, and other amenities, and we are providing them as per the city's development plan," said Shrinivas Kilje, an assistant commissioner.
"There are constraints, but it's an exaggeration to say there are no amenities or that the area is neglected," he said.
Most of such neighborhoods came about after the partition of India in 1947 as Muslims made their homes in certain areas or clustered together according to their profession, such as weavers, tanners, or potters.
Some neighborhoods in northern and western cities such as Delhi, Mumbai, and Ahmedabad sprung up in past decades in the aftermath of Hindu-Muslim riots, as Muslims came together for greater security or were pushed out of mixed neighborhoods.
Muslims, who make up 13 percent of India's population, face bias when buying or renting properties, analysts say.
The deep-rooted biases are eroding the multi-cultural nature of India's booming cities, creating neighborhoods which perpetuate the communal divide.
The divided spaces exist because of a fear of violence, and also because labor is increasingly divided in cities, with officials tacitly encouraging the segregation through discriminatory urban planning and governance, according to experts.
Some states like Gujarat, which witnessed some of the worst communal riots in the country in 2002, even have laws that restrict Muslims and Hindus from selling property to each other.
"They do not just segregate themselves: cities are hubs of capital accumulation and profit making, so the poor are discriminated against. Muslims are among the poorest," said Ghazala Jamil, an assistant professor at Jawaharlal Nehru University in Delhi.
"There is no intervention by the state to end the segregation, as it is a mode of governance, a way to manage inequality," said Ms. Jamil, citing data from her recent book on Muslim neighborhoods in Delhi.
About a third of India's population of 1.25 billion lives in cities, with tens of thousands leaving their villages every year in search of better economic opportunities, largely as construction workers, domestic helpers, and security guards.
In Mumbai, India's financial hub, more than half the population lives in slums and informal settlements. Most residents are Muslims and lower-caste Hindus.
The ghettoisation exacerbates their poverty and alienation, with even job applications and requests for bank loans often rejected because of where they live, Chatterjee said, citing interviews and data from her book.
"Even those who have the means to move from these neighborhoods usually find it hard to get a place because of their religion," she said.
"Whether the confinement is imposed directly or indirectly, it deepens the divide between Muslims and Hindus," she said.
An ambitious Smart Cities plan to upgrade cities risks marginalizing the poor further, as affordable housing options become increasingly scarce.
"Urban neighborhoods are a manifestation of labor markets, so it is a sort of economic exploitation and containment of the poorest communities including Muslims," said Jamil.
"They are often limited to the dirtiest, lowest paid jobs, and don't have much bargaining power or the ability to move elsewhere," she said.
This is the case in Mumbai, a magnet for migrants from across the country. The divide in the city grew after bloody Hindu-Muslim riots in 1992-93.
But it is also true of smaller cities such as Meerut, where Hindu residents recently forced a Muslim family to give up a house they had bought in a predominantly Hindu neighborhood, according to local news reports.
Sensitive urban planning could be a way to reduce the impact of segregation, but powerful real estate developers often lobby against integrating neighborhoods, said Chatterjee.
In time, the dominant communities begin to stereotype and turn the culture of minority communities into a commodity, with these neighborhoods even marketed as tourist attractions for their distinct cuisine or type of architecture, said Jamil.
"Going to eat or shop in the Walled City in Delhi or the Old City in Hyderabad may seem cool, but it is perpetuating the division," she said.
"As long as cities continue to be centers of capital accumulation, we will see dispossession of the poor and the powerless, who will continue to be pushed to the margin."
This story was reported by the Thomson Reuters Foundation.