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

All right. Colma.

About 10 miles south of San Francisco out toward the airport,

there's a town called Colma. I have never been to Colma before, but it's cool you can take the train right here.

That's producer Avery Truffleman. Oh, all right. Oh my God, right beyond the train station,

are already these big rolling green hills peppered with tombstones.

73% of the land in Colma is covered with graveyards.

Oh, and they're just rows and rows of big gravestones that look like little houses.

There are 17 full-sized cemeteries together in one town, 18 if you include

the pet cemetery. This is huge! It is a city of the dead, what's known as a necropolis.

We claim to be the only necropolis in the United States anyway.

The only city that is primarily dedicated to cemeteries.

This is Maureen O'Connor, president of the Koma Historical Association.

It doesn't mean that there are a lot of cities that don't have

cemeteries within their boundaries, but nothing of the concentration that we

have here. And Koma truly looks like a sprawling city, a landscape of mausoleums and monuments and towers and

tombstones that glint in the sun for as far as the eye can see.

But it is eerily quiet. Here the dead outnumber the living a thousand to one.

We have 1600 living citizens and we have about one and a half million residents who live underground or in mausoleums.

Maureen talks about her dead neighbors and her living neighbors with the same vocabulary.

Like when she referred to John Daly, the long-deceased dairy magnate.

John Daly, for whom Daly's city is named, one of our neighbors.

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