12 Cities That Quietly Fixed Something, Including Why Pittsburgh Turned On Its Streetlights by Day

For almost half a century, Copenhagen’s harbor was off-limits to swimmers. “It was forbidden from 1954 to 2002 to swim in the harbour because the water was too polluted,” architectural historian Helen Welling told The Globe and Mail in 2025.

In the 1990s, the city began a cleanup that took years. In 2002 it opened its first harbor bath, at Islands Brygge, a short walk from the city center, and more harbor baths followed. Today people swim in the harbor in every season, including winter.

Pittsburgh ran on soft coal, and its mills, railroads and home furnaces filled the air with smoke. In winter, downtown got only a third as much sunshine as the county airport seven miles away, and in the early 1940s the city turned on its streetlights during the day.

Then Pittsburgh began enforcing strict smoke rules, and businesses, railroads and households all had to comply. In the winter of 1947–48, the city got 39% more sunshine than the year before. By 1954, smoke was 90% lower than it had been in 1946.

Within a month in 1999, the Galician city of Pontevedra, population about 80,000, turned all 300,000 square meters of its medieval center over to people on foot and paved the streets with granite. Street parking went, and roundabouts replaced traffic lights.

The Guardian reported in 2018 that CO2 emissions had fallen 70% and that the center had gained 12,000 new residents while other towns in the region shrank. Those same streets have not had a single traffic accidents since 2009.

The Catharijnesingel canal has circled Utrecht’s old town since the city’s founding in 1122. In the 1970s, part of it was filled in to make room for a road with space for 12 lanes, so shoppers could drive straight into the center.

The first plans to bring the water back came in the 1990s, and in 2002 residents voted for a city plan in which water would replace roads. On Sept. 14, 2020, the restored canal reopened with pleasure boats and even a few swimmers. Boats can again travel the full 6-kilometer loop, about 3.7 miles, around the center.

The High Line was built in the early 1930s to carry freight trains above the streets of Manhattan’s West Side, loaded with meat, dairy and produce. As trucks took over, the trains stopped by the 1980s, calls to demolish the structure followed, and wild plants took over the tracks.

In 1999, two local residents founded Friends of the High Line to save it. The first section opened as a park in 2009, and more followed in 2011, 2014 and 2019. Today it is one continuous 1.45-mile greenway with more than 500 species of plants and trees.

The double-deck Embarcadero Freeway went up along San Francisco’s waterfront in the late 1950s. It cut the city off from the bay and left only the clock tower of the Ferry Building visible.

After the freeway was damaged in 1989, the city chose to remove it instead of repairing it, and it came down in 1991. A waterfront boulevard and promenade took its place. The Ferry Building got a 10-year, $110 million renovation, and its long central hall is now a public promenade lined with local food shops. The planning group SPUR calls it one of the city’s greatest planning success stories.

For decades, the elevated Central Artery cut downtown Boston off from its waterfront. A huge project that began in 1991 replaced it with a highway underground and freed more than 300 acres of land for 45 parks and public plazas.

The centerpiece, the Rose Fitzgerald Kennedy Greenway, opened in 2008. It is a 17-acre park stretching 1.5 miles through Chinatown, the Financial District, the Wharf District and the North End, and almost 900 trees line it.

After the M-30 ring road was built in the 1970s, Madrid’s Manzanares River was squeezed between traffic lanes on both banks. Between 2003 and 2007, the city buried the riverside stretch of the highway in tunnels.

On top, the Madrid Río project laid out about 300 acres of parks along 3 miles of river, with footbridges, fountains, playgrounds and even a beach of sorts. Its chief architect told The World in 2016 that 33,000 trees and 460,000 shrubs had been planted, many in only five feet of soil over the tunnels.

In Comuna 13, a neighborhood that clings to a steep hillside in Medellín, Colombia, getting home meant climbing hundreds of steps. City officials compared the climb to going up a 28-story building, and on foot it took about 35 minutes.

In December 2011, the city opened a $6.7 million outdoor escalator in six sections, 1,260 feet long, with one escalator going up and another going down. Officials said it would cut the trip to about six minutes.

In Bishan-Ang Mo Kio Park, the Kallang River used to run through a concrete canal along the park’s southern edge. Singapore’s water agency demolished the canal and replaced it with a natural, meandering river, which opened in 2012.

Plants, rocks and soil now hold the banks in place, a method called soil bio-engineering that had never been tried in Singapore before. In heavy rain, the parkland beside the river is designed to flood and carry the extra water. The rest of the time, people can walk right down to the water.

Harbor Drive, a freeway built along Portland’s riverfront in 1943, kept people away from the water. When the state proposed widening it, a 1968 task force recommended closing it instead and going back to a 1903 park plan by the Olmsted Brothers.

Harbor Drive closed for good in 1974, and the waterfront park has welcomed visitors since 1978. Tom McCall Waterfront Park now covers 30 acres and is often cited as the first freeway removal in the U.S.

The Walnut Street Bridge, built in 1890, was the first non-military highway bridge across the Tennessee River. In 1978 it was closed to cars as unsafe, and the state recommended tearing it down.

Residents pushed back. Federal money meant for the demolition went to restoration instead, and local fundraising brought in another $2 million. Work on the 2,376-foot span ran from 1991 to 1993, and when it reopened, it was the longest pedestrian bridge in the world.