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

If you've wandered at Machu Picchu or Stonehenge or the Colosseum or even snuck into that abandoned house on the edge of town, you know the power and a piece of decrepit architecture.

Even if you haven't been to these places, they've been photographed and filmed for you.

Abandoned Soviet bus stops, deserted old movie theaters, decaying residential streets. They're fascinating in this like planet of the apes kind of way.

So of course, there's a German word for it.

Ruinenlust, the longstanding aesthetic obsession with decay.

Resident Germana file and producer Avery Trouffleman.

It might actually be one of those made up German words, it probably is.

But the concept itself is totally a real thing. Ruins inspire wonder.

They give the mind this task of reconciling what's there and what's not.

What once was and what now is.

People flock to remainders of ancient civilizations.

Romans, the Mayans, the Egyptians. But people also flock to things that just look like they're ancient too.

That combination of decomposition and romance makes a perfect cocktail of repulsion and allure.

And for San Francisco's, this place is Sutro Baths.

My friend Austin brought me there one night. So how do you get in? Does the trail just lead right to it?

Yeah, yeah, there's steps. There's a parking lot up there and steps up the ground.

Head to the rocks at Lanzan on the very northwest corner of San Francisco.

Walk down the flight of stairs into a grassy slope that hugs the sea.

Off to the right is the gaping maw of a cave.

To your left is the crumbled foundation of a concrete structure.

It looks like a giant Belgian waffle, about seven feet tall and 50 feet wide on the longest side.

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