1.You've probably definitely seen the outside of the Taj Mahal in India. It looks like this:

But if you've ever wondered what the inside looks like, here you go:

The Taj Mahal was built by Mughal Emperor Shah Jahan in memory of his wife. It was completed in 1653.

According to UNESCO, the Taj Mahal was planned to be a perfectly symmetrical building. Pretty cool!

2.The outside of St. Basil's Cathedral in Moscow is imprinted onto my brain:

But the inside is just as intricate:

The cathedral was commissioned by Ivan the Terrible in 1555.

It's actually composed of 10 churches.

And, get this, the exterior was originally painted white!

3.I'm sure you've seen the outside of Cinderella's Castle at Disney World in Florida.

But did you know there's an entire suite in it?

Disney sometimes offers stays in Cinderella's Castle suite as prizes in contests and sweepstakes.

Below the suite (also inside the castle) is a full-service sit-down restaurant called Cinderella's Royal Table. No need to win a sweepstakes to make a reservation here and get into the castle!

4.Listen, I wanted to find out what it looked like inside the Great Pyramid of Giza, but I couldn't find pictures. This, however, is the Pyramid of Djoser, also in Egypt. It looks exactly like a step pyramid on the outside.

But check out all of the tunnels on the inside:

This step pyramid has an array of tunnels, false entrances, and galleries.

The Pyramid of Djoser was the first pyramid built in Egypt, and it marked the beginning of their ambitious pyramid-building program.

5.You most certainly know what the Leaning Tower of Pisa in Italy looks like from the outside:

But did you know you could go into it?

The Leaning Tower of Pisa was actually a Nazi base during WWII due to the vantage point they could get from the top. When American troops were instructed to destroy all enemy buildings, they couldn't bear to destroy the tower because of its aesthetic charm.

6.You can't argue that La Sagrada Familia in Spain is stunning from the outside.

But I bet you had no idea how stunning it was from the inside.

Architecturally, La Sagrada Familia isn't done. More additions are planned for 2022.

This means that over 135 years after laying the first stone for the basilica, La Sagrada Familia is still being built.

7.You've seen the outside of the Louvre in Paris and its iconic glass pyramid designed by I.M. Pei.

But here's what the inside of that famous pyramid looks like:

This glass pyramid was inspired by the Great Pyramid of Giza.

It was made to accommodate the increasing number of visitors to the Louvre.

8.I'm sure you've seen what the outside of the Hagia Sophia in Istanbul looks like.

But a view from the outside, to me, makes it look deceptively small.

However, it is huge. The crown of the dome is 180 feet above the floor.

The dome actually collapsed shortly after construction, as its weight couldn't be beared by the structure. After reconstruction, the dome hasn't had another collapsing incident in 1,400 years.

9.Surely you've seen the outside of Big Ben in London.

But did you know there was a spiral staircase going to the tippy top?

As of 2010, only residents of the UK can go inside the clock tower.

Even then, you have to be sponsored by a member of Parliament of the House of Lords.

10.I'd be surprised if you didn't know this was the outside of the Sydney Opera House in Australia.

But here's what it looks like looking out from those big windows!

Construction of the Opera House was supposed to take four years. However, it took 14.

There was a competition to design the Opera House and, out of the 233 contestants, Jørn Utzon from Denmark won.

11.I'm sure you've seen it, but here's what Angkor Wat in Cambodia looks like from the outside.

I doubt you've seen what it looks like on the inside:

The temple spreads across 400 acres and is said to be the largest religious monument in the world.

Its name literally translates to "temple city" in the Khmer language.

12.It's safe to assume you've seen the Statue of Liberty in New York City from the outside.

Here's what she looks like on the inside:

In 1865, Frenchman Édouard de Laboulaye came up with the idea to gift Lady Liberty to the US.

He had help designing the massive iron pylon and secondary skeletal framework from Gustave Eiffel. That's right! Eiffel worked on Lady Liberty before making his famous tower.

13.You know what Chichen Itza in Mexico looks like, right?

Well, here's what the inside looks like, and it's the only picture I could find. This is the throne room.

14.You've seen the outside of the Acropolis in Athens, Greece:

And although the inside doesn't look like much anymore...

Here are artist renderings of what it would have looked like with a roof...

...and without. Pretty interesting, huh?

15.If you've seen Indiana Jones and the Last Crusade, you've seen the city of Petra in Jordan:

While there isn't a holy grail inside, it's interesting to see the carved rock work:

Petra is known as the Rose City for the color of the stones that key buildings are carved out of.

16.I'm sure you're familiar with the outside of the Roman Colosseum in Italy.

But, I'm going to say it, the inside looks more spectacular than the outside:

The Colosseum has 80 entrances and can fit 50,000 spectators.

It's also complete with underground passages where gladiators and animals were kept before being sent into the arena.

Some 36 trap doors led from the arena to these passages and were used for special effects.

17.You've probably seen the outside of the Forbidden City in Beijing, right?

But the inside of the palace is a sight to be seen:

The Forbidden City is composed of more than 90 palace compounds.

It was home to 24 emperors and their families until 1925, when Puyi was expelled for the Forbidden City to turn into the Palace Museum.

Now, as the Palace Museum, minor palace buildings have works from the Imperial Gallery on display, and the Forbidden City is open to tours from the public.