You can tell a lot about a city by looking at its skyline.

Over the decades, many cities have exploded in size and have introduced ambitious works of architecture to the world.

Two decades ago, Dubai was a relatively undeveloped city. Now it’s filled with gleaming skyscrapers. And cities like Toronto look virtually unrecognizable compared to a century ago.

Here are some cities whose skylines look completely different, several decades later.

The permission to use some of these photos were obtained through RENTCafé. Article copyright: www.insider.com.

Then: New York City

Here’s the New York City Skyline in 1964, from across the Brooklyn Bridge.

Now: New York City

In 2016, One World Trade Center dominates lower Manhattan.

Then: Dubai

In 2000, Dubai’s Marina area was mostly dirt.

Now: Dubai

It’s grown quite a lot.

Then: London

London’s Westminster area in the late 1920s.

Now: London

Here it is in 2012. It’s got some new landmarks, like the London Eye Ferris wheel.

Then: Abu Dhabi, UAE

Abu Dhabi’s beach in 1961 featured just water distillation plants.

Now: Abu Dhabi, UAE

Now it’s a place for tourists, with gleaming skyscrapers in the background.

Then: Paris

This is the view from the Eiffel Tower in Paris when it was built, in 1889.

Now: Paris

Today, the city is crowded with more buildings.

Then: Doha, Qatar

Doha, Qatar looked like this in 1977.

Now: Doha, Qatar

Here’s the skyline today.

Then: Sydney

From Sydney’s Harbour Bridge, you can see the skyline of the city. Here it was in the 1930s.

Now: Sydney

The skyline has grown significantly since then, with some of the largest buildings in Australia.

Then: Tokyo

In 1976, Tokyo’s skyline was busy and the city was thriving.

Now: Tokyo

It’s grown only more since then.

Then: Hong Kong

Hong Kong’s buildings in 1957 were tall for their day.

Now: Hong Kong

Now they’re even taller, made with plenty of glass and steel.

Then: Rio de Janeiro

This photo was taken sometime around 1930, when “Christ the Redeemer” was in construction.

Now: Rio de Janeiro

The city is much more developed today – and the statue looms over it all.