Here’s Why There’s a Black Square on the Ceiling of Grand Central Terminal

If you’ve ever passed through New York City’s bustling Grand Central Terminal, you’ve likely marveled at the grand beaux-arts architecture, iconic four-faced brass clock and constellation ceiling mural. But if you look closely, you’ll notice something else: a small, uncleaned black spot.
The dark patch on the terminal’s ceiling is located near the constellation Cancer and has baffled visitors and sparked curiosity for years.
The ceiling of Grand Central Terminal, completed in 1913, is a famous depiction of the zodiac constellations and nearby stars.
But over the years, the mural suffered damage from leaks, grime and air pollution. By the 1940s, it was so obscured by dirt that the New York Central Railroad covered it with boards and repainted the stars, but the boards themselves became covered with dirt from the hordes of passengers coming through the terminal each day.
By the late 1980s, Grand Central Terminal was in desperate need of restoration, and in 1988, the Metropolitan Transportation Authority commissioned a $113.8 million renovation to revitalize the terminal’s interior.
Renovations spruced up the interior of the terminal, cleaning the ceiling mural, and removing the prominent Newsweek clock installed in the 1950s that was blocking light into the space.
The ceiling mural had endured decades of accumulated dirt, pollutants, and most notably, cigarette smoke.
Despite painstaking work to clean the ceiling during the restorations, a small 9-inch x 18-inch section of the ceiling near Cancer on the mural was left uncleaned.
The decision to leave this dark spot untouched was intentional, and today it serves as a reference point for future preservationists, showing the mural’s condition before restoration. It’s also a visible reminder of just how much dirt and grime—mainly from cigarette smoke—had accumulated over the years.
Today, there is thankfully more focus on the environment and air quality for the more than 700,000 passengers that pass through the terminal every day.
In 2003, New York City enacted a comprehensive ban that prohibited smoking in most indoor public places and workplaces, including bars and restaurants.
While earlier this year the city implemented Local Law 97. Also known as New York City’s Green New Deal Law, it sets existing large buildings on a path to eliminating emissions by 2050. It also aims to reduce building emissions, which are responsible for 70 percent of the city’s greenhouse gas emissions.
Meanwhile, the city also aims to reduce disparities in ambient pollution level exposures by 20 percent for PM2.5 particles and 50 percent for sulfur dioxide by 2030 relative to 2013 levels.
Today, this spot is a quirky attraction, with countless TikTok and Instagram posts, and YouTube videos speculating about its origins. So next time you’re one of thousands of people passing through the iconic terminal, don’t be surprised if you see a group of people looking up in search of the uncleaned ceiling spot.