This is 99% invisible. I'm Roman Mars.

In the Temple Hofschneberg District of Berlin, there's an enormous concrete structure that sits across the street from a supermarket.

It's obscured by trees, surrounded by residential apartments, and gently flecked with German graffiti.

Okay, check one, two, one two.

It is 8.34 a.m.

I am quite possibly the most jet lagged I've ever been in my entire life,

and I'm waiting for my Uber, or as they say, here in Germany, my Uber.

We sent 99PI producer Vivian Lay there to check it out.

Jetlag be damned, I met up with Hana Fisha and Vincent Brookman.

Hannah is the curator and deputy director for the Temple Hofshunaberg museums,

and Vincent is a journalist and tour guide.

They were there to show me around a curious neighborhood landmark.

From afar, it kind of looks like a derelict, brutalist grain silo.

Is it a popular site for people to visit this one?

Yes.

It's the most popular.

And it is the least aesthetically pleasing.

Yeah, that is true.

Yeah.

This structure is a bit hard to describe

because there's literally nothing else like it in the world.

On the surface, it's a very, very big,

...