America's cities may be home to individuals belonging to thousands of cultural groups and myriad socioeconomic statuses. But these urban centers are surprisingly no melting pot. As Nate Silver pointed out in several infographics, diverse cities are often the most segregated, especially at the neighborhood level.

To add to this gloomy reality, today's urban developers often use subtle tactics to keep cities economically and racially divided. "The fair housing laws passed in the last half-century have forced racists to devise whole new methods of discrimination, subtler but serving the same purpose: to keep people of color out of 'white' spaces," author Daniel Kolitz wrote on the online culture publication Hopes & Fears.

Here are 5 places you might not have noticed racism crops up in your city's landscape.

1. Pollutants isolated near low-income neighborhoods.

In 2012, the National Institute of Environmental Health Sciences published a study revealing how racial and economic equality impact who suffers from dangerous air pollution.

"The greater the concentration of Hispanics, Asians, African Americans, or poor residents in an area, the more likely that potentially dangerous compounds such as vanadium, nitrates, and zinc are in the mix of fine particles they breathe," Environmental Health News reported, in a summary of the study findings.

Those exposed to the largest numbers of dangerous pollutants were Latino, according to the report, while those with the lowest were white.

What's causing this discrepancy? "Due to high housing costs and historical discrimination, low-income and minority neighborhoods are clustered around industrial sites, truck routes, ports and other air pollution hotspots," the report explained.

2. The construction of Chinatowns

In cities like New York, Boston, San Francisco, and Los Angeles, tourists and local residents flock to Chinatown enclaves to glimpse ornate pagodas and try favorite dumpling spots. But the initial reason these neighborhoods cropped up has been largely forgotten.

Many Chinese immigrants flocked to the the West Coast of the U.S. in the mid-1840s, when "following defeat by Britain in the first Opium War, a series of natural catastrophes occurred across China resulting in famine, peasant uprisings and rebellions," PBS reported. Chinese immigrants were initially welcomed to San Francisco with open arms, and even praised for their work ethic by Mayor John W. Geary during an 1850 ceremony, according to PBS. But it wasn't long before Americans began to view the Chinese immigrant workforce as a threat.

"These immigrants were paid lower wages than white workers, who then blamed Chinese laborers for driving down pay and taking away jobs," the Huffington Post reported. "After the railroad was completed and white laborers in other industries began to fear for their jobs, anti-Chinese attacks increased, including beatings, arson and murder."

In San Francisco, Chinese workers were driven into the neighborhood now known as Chinatown by racism and legislation that prohibited them from living in other parts of the city. There were also 153 anti-Chinese riots in the American West in the 1870s and 1880s, the Huffington Post reports, which led some Chinese immigrants to flock to the East Coast, where other Chinatown neighborhoods emerged in cities like New York and Boston.

“In the broadest strokes, Chinatowns were products of extreme forms of racial segregation,” Ellen D. Wu, a history professor at Indiana University Bloomington and author of "The Color Of Success: Asian Americans And The Origins Of The Model Minority" told the Huffington Post. “Beginning in the late 19th century and really through the 1940s and ‘50s, there was what we can call a regime of Asian exclusion: a web of laws and social practices and ideas designed to shut out Asians completely from American life.”

Beginning in the 1950s, San Francisco's Chinatown was rebranded with help from publications like Readers Digest, which painted the idea of strict Chinese, households as a counterpoint to growing worry about delinquency among white youth, the Huffington Post reported.

This fed into the neighborhood's initial allure as a tourist attraction. “The San Francisco Chinatown gate was only built in 1970,” Wu told the Huffington Post. “Even in some of the promotional literature about why you should visit Chinatown, they say, come visit and see our model families, see our children who never get into trouble and love to study.”

But the new image of Chinatowns also drew developers, who closed down local shops, houses, and apartment buildings to accommodate high end businesses and upscale condos virtually unaffordable to the immigrant populations who historically inhabited the neighborhoods.

“Chinatowns are turning into a sanitized ethnic playground for the rich to satisfy their exotic appetite for a dim sum and fortune cookie fix,” Andrew Leong, the co-author of a 2014 report published by the Asian American Legal Defense And Education Fund, told the BBC.

3. Hostile Architecture

As ATTN: has previously reported, urban structures can be used to deter homeless populations and conceal poverty.

At its most vicious, hostile architecture can turn up in spikes that prevent homeless people from sleeping on city streets and in public parks. But hostile architecture can also take shape in bench dividers, strategically placed plants, and other elements meant to keep society's perceived undesirables out of sight.

"We see these measures all the time within our urban environments, whether in London or Tokyo, but we fail to process their true intent," writer Alex Andreou wrote on the Guardian. "I hardly noticed them before I became homeless in 2009."

4. Lack of public transportation

Transportation has long factored into the fight for racial equality, and extends far beyond seating on public buses. "New York City was famously shaped by the powerful urban planner Robert Moses who, along with being a visionary, was demonstrably racist," Hopes & Fears observed.

The New York Times described author Robert Caro’s biography of Moses, which aptly captures why Moses’ legacy is so controversial:

"'The Power Broker: Robert Moses and the Fall of New York,' documented many of what he regards as Moses’ transgressions, like acres of sterile public housing towers, parks and playgrounds for the rich and comfortable, and highways that sundered working-class neighborhoods and dispossessed a quarter of a million people.”

Today, the city's subway lines preserve racial divides by isolating residents of primarily non-white areas, like the Eastern Rockaways, and a lack of direct public transportation options connecting historically non-white neighborhoods in Brooklyn, Queens, and the Bronx, Gothamist pointed out.

A March 2016 study conducted by the think tank Center for an Urban Future found that residents of Queens — which has large Black, Hispanic, and Asian populations — had the longest commutes in the city.

Los Angeles' public transit history has also seen a good deal of controversy. In the mid 1990s, the Bus Rider's Union (BRU) in Los Angeles worked to raise awareness of how the city's scant public transit options impacted bus riders — 80 percent of whom were people of color, the NAACP's Legal Defense Fund pointed out at a 1994 MTA meeting, KCET reported.

In 1994, the BRU and LDF presented a lawsuit to the MTA alleging that the MTA was "intentionally discriminating against racial and ethnic minority groups in the delivery of transportation services" paid for with federal funds. In 1996, a court injunction required the MTA to reform the LA bus system.

Many believe that the actions of Bus Riders Union majorly shaped the Metro lines in today's Los Angeles.

"While today's Metro Orange Line Bus Rapid Transit might not be wholly a result of these efforts, no doubt it benefited from these debates," KCET observed.

Racially charged disputes between local residents and transit authorities happen across the country.

"Wealthy, mostly white residents of the northern Atlanta suburbs have vocally opposed efforts to expand the Metropolitan Atlanta Regional Transit Authority subway system into their neighborhoods for the reason that doing so would give people of color easy access to suburban communities," Hopes & Fears reported. "The lack of public-transit connections to areas north of the city makes it difficult for those who rely on transit—primarily the poor and people of color—to access job opportunities located in those suburbs."

In January 2014, a Dayton, Ohio bus line saw major online backlash for linking predominantly Black neighborhoods to predominantly white suburbs.

"They resented—sometimes in purely racist terms—that this new public transportation line would be bringing outsiders, largely blacks, to Beavercreek, a suburb that is about 89 percent white," reporter Corinne Ramey wrote on Slate.

Often public transportation simply caters to those living in urban centers, which proves especially limiting for low-income populations living outside of cities.

"The number of suburban poor increased by more than 60 percent between 2000 and 2012 according to the Brookings Institution, and public transportation systems have yet to catch up," Ramey pointed out. "For those without cars—according to 2013 U.S. Census data, 15.9 percent of blacks and 9.1 percent of Hispanics live in households without cars, compared to just 5 percent of whites—public transportation is not a convenience, but a necessity."

5. Highways as dividers.

In many areas of the country, highways are used to isolate low-income neighborhoods from wealthier areas, which can underscore racial divides.

“Highways have often been placed centrally in cities in order to eliminate low-income areas and reshape the landscape of the American city,” Hopes and Fears reported. “New Orleans, Miami, Omaha and Charleston, West Virginia are just some examples of places where the highway has become a bulldozer. The Supreme Court has upheld that "urban blight" is an acceptable reason for eminent domain to be used.”

Author Eric Avila chronicled how race shaped highway construction in postwar America in his book "The Folklore of the Freeway: Race and Revolt in the Modernist City," an excerpt of which has been published on Alternet.

"In many southern cities, local city planners took advantage of federal moneys to target black communities point-blank; in other parts of the nation, highway planners found the paths of least resistance, wiping out black commercial districts, Mexican barrios, and Chinatowns and desecrating land sacred to indigenous peoples," Avila wrote. "The bodies and spaces of people of color, historically coded as 'blight' in planning discourse, provided an easy target for a federal highway program that usually coordinated its work with private redevelopment schemes and public policies like redlining, urban renewal, and slum clearance."