VO: Some have called Unity Temple in Oak Park Frank Lloyd Wright's masterpiece.

Wright wowed visitors from the moment they entered with an age-old architectural trick called compression and release.

- [Heidi] We entered the lobby from outside, and we're already being compressed down into the space.

- [Geoffrey] Look how low that is.

- [Heidi] Now as we're entering the cloister, the ceilings get lower and darker.

- I can almost touch it.

- Yeah, and it's compressing you down.

And then go ahead.

- Okay.

- You get released into the sanctuary.

- [Geoffrey] Oh my gosh.

Wow!

- [Heidi] And Frank Lloyd Wright called this his Noble Room.

So you're being risen up almost to nobility.

And it just opens right up, and so much to look at.

- The Noble Room?

- The Noble Room.

- That sounds like Frank Lloyd Wright.

- It does, yes.

It does.

- Modesty.

- Very modest man, yeah.

- [Geoffrey] And what year was this built?

- So it was finished in 1908.

And he designed it more in 1906.

- So let's put that in context.

What do houses of worship look like in 1908?

- [Heidi] Well, probably what a lot of them look like today, more Gothic, more traditional steeples, heavy stone and mosaics but the minister at the time, he wanted something different, and to reflect the Unitarian values and ideals of community.

- [Geoffrey] So how does this reflect Unitarianism?

- Well, as you can see, we are here in the round.

The seating is not your traditional church seating of front to back pews.

So that way, you can see people that you're communing with.

And community is really important in Unitarianism.

- [Geoffrey] So talk about the materials in here.

It's not a typical color palette for a house of worship, I don't think, right?

- [Heidi] Here he really wanted to bring nature in, and he said he wanted the sanctuary to feel like it was a happy cloudless day at any point in time.

The soft yellow that he brings in really reflects the light, and I love how he brings the light in, because we don't have any windows that are at human eye level, so with the clear story windows, you get a lot of indirect light.

- [Geoffrey] Up at the top.

- [Heidi] And then of course the beautiful stained glass windows in the ceiling.

There's 25 of them, filter light down.

And that's supposed to represent nature in an abstracted flower, so while you're standing here, you can almost feel like you're sitting underneath a field of flowers.

- [Geoffrey] So the outside of the building is made of?

- Concrete.

- And that was very revolutionary, right?

- It was.

Unity Temple's one of the first public buildings to use concrete in this way.

It was poured in place, and then when we moved to the inside, there is some concrete, but also plaster.

And there's a whole technique that he used of creating texture in the plaster, and when he painted it, you could see, especially when you get up to the ceiling, lights and darks, and kind of a stippled finish, and it really is almost suede like.

- [Geoffrey] Even in the skylight wells there, you can really see it.

- [Heidi] Absolutely.

VO: Wright lived and worked in Oak Park for 20 years.

The village has more Wright buildings than any place in the world.

His prairie style matured here, as did his reputation for arrogance.

He could rightfully claim to be the greatest architect of his day.

But not the greatest at engineering durability into his designs.

The years took their toll on Unity Temple.

By 2000, it was named one of the 10 most endangered buildings in Illinois.

- [Heidi] This building is pretty difficult to maintain, like a lot of large buildings, but being that this- - [Geoffrey] A lot of Frank Lloyd Wright buildings.

- [Heidi] A lot of Frank Lloyd Wright buildings, yes.

In fact, I think it was a few years before the restoration, a big section of the ceiling had fallen, so there was a lot of patching.

And then more aesthetically, a lot of the paint wasn't quite right.

All this beautiful stippling, and the texture have been painted over so many times.

- [Geoffrey] What was done in the course of the restoration?

- Yeah, if you can imagine, this whole building was wrapped in plastic, and scaffolded everywhere.

Every single piece of trim work was removed, and cataloged, and refinished, and reinstalled.

It ended up being about $25 million to do the full comprehensive restoration.

VO: With restoration completed, Unity Temple was named a UNESCO World Heritage Site, along with seven other Wright buildings across the country, putting it in a league with the Egyptian pyramids, the Great Wall of China, and the Vatican.