Some of the world’s most iconic skylines are photographed so often that it's almost impossible to imagine them looking any different than they do now. But even New York City, Hong Kong and London have been altered over the decades. The changes were spurred by economic success (or lack thereof), major historic events, population growth or shifting cultures.

For some places, the “then” in the “then and now” equation was only a few decades ago. Many of London’s most visible modern landmarks, for example, are less than 20 years old. Other places have a mixture of buildings, creating an architectural timeline that offers a visual story of the city’s history.

Here are 10 cities where you can see dramatic differences and surprisingly similarities between “then” and “now.”

New York City

Then: Though new buildings have been constructed since the 1930s, New York City has always been known for its dense skyline. Now: New skyscrapers are springing up, but iconic older buildings still remain. THEN: Though new buildings have been constructed since the 1930s, New York City has always been known for its dense skyline. NOW: New skyscrapers are springing up, but iconic older buildings remain. (Photo: Wikimedia Commons; TTstudio/Shutterstock)

New York City defines the term “urban.” The city’s skyscraper era began with the construction of the World Building in 1890. From World War I through the 1930s, tall buildings rose in the Big Apple at a rapid rate. This period saw the construction of iconic structures like the Empire State Building and the Chrysler Building. More than a dozen of the city’s most recognizable skyscrapers opened during this era, even some that don't exist today.

New York City will continue to evolve in the future. Several new projects are in the works. Though the details have changed and will continue to change, the skyline, especially in Manhattan, has always been recognizable because of its dense layout.

Shanghai

Then: The Bund was a major center of commerce in the 1920s. Now: Though other areas of Shanghai have been totally modernized, the historic buildings of the Bund remain intact. THEN: The Bund was a major center of commerce in the 1920s. NOW: Though other areas of Shanghai have been modernized, the historic buildings of the Bund remain intact. (Photo: Wikimedia Commons; chuyuss/Shutterstock)

Shanghai has come to represent the country's modernization and economic success. The 2,000-foot Shanghai Tower is now the world’s second tallest building, and dozens of other constructions have sprung up since the turn of the century. Shanghai currently has more than 1,000 buildings that are 30 stories or higher.

One of the most recognizable and historic areas of the city has changed little in the past century. The Bund, along the Huangpu River, features Beaux Arts buildings that were used as banks and trading houses when Shanghai was the economic gateway to China for foreign trading powers during the early 1900s. The riverfront area was altered recently to make it more accessible to tourists. The 50-plus buildings along the Huangpu still remain as a reminder that this isn't the first time Shanghai has been the economic center of East Asia.

Hong Kong

Then: Hong Kong’s skyscraper boom had not yet started in the 1960s. Now: Hong Kong Island now has a forest-like collection of high-rises. THEN: Hong Kong’s skyscraper boom had not yet started in the 1960s. NOW: Hong Kong Island now has a forest-like collection of high-rises. (Photo: Wikimedia Commons; Sean Pavone/Shutterstock)

Hong Kong is often referred to in the same breath as New York City when it comes to iconic skylines and skyscrapers. The territory has more than 300 buildings that are 500 feet or taller. Hong Kong is just as recognizable for its natural elements, including mountains that rise up behind the most densely built-up areas on Hong Kong Island.

Hong Kong looked very different in the 1960s. Though high-rises were starting to pop up in what was then a British territory, the skyline looked nothing like it does today. Building booms in the 1970s and again in the late ‘90s and early 2000s gave Hong Kong its current landscape. Interestingly, it was geography more than anything else that caused the skyscraper renaissance. Because of the mountains and the harbor, land space is limited. Hong Kong now has more people living above the 15th floor of residential buildings than any other place on Earth.

Havana

Then: This photo, taken in 1900, shows architecture that might look familiar to people who visit present-day Havana. Now: Some streets in Old Havana have been restored, but others have not. THEN: This photo, taken in 1900, shows architecture that might look familiar to people who visit present-day Havana. NOW: Some streets in Old Havana have been restored, but others have not. (Photo: Libby norman/Wikimedia Commons; Library of Congress/Wikimedia Commons)

If a growing skyline is a sign of economic success, than an unchanging one must point to stagnation. Some cities have placed value on their historic buildings (the Bund in Shanghai, for example), but for other places, construction ground to a halt because of an economic slump. Havana’s skyline has changed in recent years, but many of the buildings are the same structures that stood in the city before the communist revolution at the end of the 1950s. Cuba struggled economically because of trade embargoes and the collapse of its greatest ally, the Soviet Union, in the early 1990s.

Newer buildings, such as the Melia Cohiba (built in the 1990s) are a part of Havana’s cityscape, but pre-revolution and colonial era architecture still define the city. This is certainly the case in Habana Vieja (Old Havana), the downtown area. The more affluent Vedado district has a few newer buildings, but many of its taller structures date back to the 1950s or before. Havana seems to be finding value in its older neighborhoods. Parts of Habana Vieja have already been restored.

Singapore

Then: Traditional architecture ruled in Singapore in the 1960s. Now: Singapore’s economic success has spurred an almost-continuous building boom since the 1980s. THEN: Traditional architecture ruled in Singapore in the 1960s. NOW: Singapore’s economic success has spurred an almost-continuous building boom since the 1980s. (Photo: John Laurie/flickr; Sean Pavone/Shutterstock)

Singapore is another Asia Pacific economic success story. A former British colony like Hong Kong, the city-state saw a building boom in the 1980s as it started to rise through the ranks of the region’s economic powers. The three tallest buildings in the country, all 920 feet, were built during these early years of wealth.

Because of its relatively small area, space is at a premium in Singapore. The one- and two-floor traditional homes and shophouses that once defined the country have been largely replaced with high-rise condos. Shophouses still stand in the Katong and Chinatown districts (as well as in a few other places around the city), but Singapore as a whole looks nothing like it did in the 1960s.

London

Then: In the 19th century, London was a crowded city known for its densely-packed rooftops, but it lacked tall buildings. Now: a relatively recent building boom has added new landmarks to London’s skyline. THEN: In the 19th century, London was a crowded city known for its densely-packed rooftops, but it lacked tall buildings. NOW: a relatively recent building boom has added new landmarks to London’s skyline. (Photo: National Library of Ireland on the Commons/Wikimedia Commons; Christine Matthews/Creative Commons)

London has a complicated history with tall structures. The famous Tower of London dates back to the 11th century. Part of the complex called the White Tower was 89 feet tall — a skyscraper by Middle Age standards. However, because of height restrictions, the city’s skyline has long been relatively flat, with Saint Paul’s Cathedral standing as the tallest building (at 364 feet) for more than 250 years.

Because of this lack of high buildings, modern additions to the London skyline have quickly become synonymous with the city. The Shard, currently the tallest structure in London, 30 St. Mary Axe and other buildings constructed since 2000 (or since 1999 if you include the now-iconic London Eye) have given the city a new look. That said, many parts of London are relatively flat, just as they have been for centuries.

Vancouver

Then: A century ago, Vancouver was a modest coastal town. Now: Now: Thanks to a unique approach to urban planning, mixed-use high-rises dominate the skyline. THEN: A century ago, Vancouver was a modest coastal town. NOW: Thanks to a unique approach to urban planning, mixed-use high-rises dominate the skyline. (Photo: William McFarlane Notman/Wikimedia Commons; Gary/Wikimedia Commons)

Vancouver has become a city of high-rises. It has more tall buildings, per capita, than any other large city in North America. This is mainly due to the Canadian city’s approach to urban planning, which involves creating livable spaces in high-density areas. Mixed use buildings, with residential and commercial space, have become common in Vancouver since the 1990s. The city’s tallest building, Living Shangri La, is an example of the commercial, office and condo combination that defines many tall buildings in Vancouver.

A century ago, Vancouver looked nothing like it does today. The North Shore Mountains were the most visible landmark. Even though lots of construction has taken place, the peaks and the coastline are still visible because special zoning rules have created corridors so that many residents can still see the skyline despite the tall buildings.

Atlanta

Then: Peachtree Street was an important commercial thoroughfare in Atlanta in the late 1800s. Now: Today, Peachtree has a mixture of historic and newer buildings. THEN: Peachtree Street was an important commercial thoroughfare in Atlanta in the late 1800s. NOW: Today, Peachtree has a mixture of historic and newer buildings. (Photo: Wikimedia Commons)

After the Civil War decimated the area, Atlanta developed into a major city during the Reconstruction era. One of the city’s main corridors, Peachtree Street, has been a commercial area and a place of urban development since these early days. In the 1980s and early 1990s, Atlanta experienced a building boom that gave the city a modern, urban edge. Seven of the eight tallest buildings in the city were built during this time.

The two tallest suburban buildings in the country, both part of the Concourse Corporate Center in Sandy Springs, are located within metro Atlanta. Despite the building boom in the ‘80s and ‘90s, Atlanta’s Downtown still has some impressive historic buildings including the Flatiron Building, constructed in the 1890s, and the Hurt Building, completed in the 1920s.

Phoenix

Then: In the 1940s, Phoenix only had a handful of high rises. Now: The skyline of downtown Phoenix has been growing since the 1970s. THEN: In the 1940s, Phoenix only had a handful of high rises. NOW: The skyline of downtown Phoenix has been growing since the 1970s. (Photo: Wikimedia Commons; Mark Skalny/Shutterstock)

When it comes to skyscrapers, Phoenix, Arizona is not near the top of the list of American cities in terms of density of buildings. However, downtown stands out against the surrounding desert and residential areas.

Phoenix had a modest skyline until a building boom in the 1960s and ‘70s. The two current tallest buildings in the city, Chase Tower and US Bank Center, were constructed in the 1970s. Phoenix has several skyscraper projects underway. However, the metro area is rather decentralized, so a lot of development has taken place in suburbs like Scottsdale, Chandler, Mesa and Tempe, which have become cities with their own list of impressive buildings.

Miami

Then: The Fontainebleau has been a Miami icon since it first opened in the 1950s. Now: The Fontainebleau sits amid a mixture of older and newer buildings in Miami Beach. THEN: The Fontainebleau has been a Miami icon since it first opened in the 1950s. NOW: The Fontainebleau sits amid a mixture of older and newer buildings in Miami Beach. (Photo: Wikimedia Commons; Felix Mizioznikov/Shutterstock)

Miami has more than 70 high-rises that stand more than 400 feet above street level. Most of the city’s tallest structures were built after 2000. For half of the 20th century, the 28-floor Dade County Courthouse was the tallest building in the city. Now, residential high-rises and hotels — including the city’s tallest building, the Four Seasons Miami — dominate the skyline.

Despite this new skyline, parts of the city have changed little since before the building boom. The Fontainebleau Hotel is one example of the architecture of Miami’s earlier heyday (when South Florida was just coming into its own as a major tourism destination). The Art Deco areas near South Beach also hearken back to this era. So while Miami’s skyline has changed, parts of the city have still retained a sense of history.