Siggi Rafn Hilmarsson is an Icelandic baker with an unconventional oven.

He bakes bread by burying it underground, where it's heated for 24 hours by nearby hot springs.

It's very common to see hot springs here in Iceland.

There is constant lava crawling under us.

This lava is heating up water, and this water comes boiling up on the surface.

We could put it in the oven, but this is much more fun.

Iceland is one of the most volcanic regions in the world, with 30 active volcanoes at any one time.

That helps create an abundance of hot springs.

Some with boiling hot water, and Siggi uses them to his advantage.

He specializes in baking hverabraud,

a traditional Icelandic rye bread recipe

that dates back hundreds of years.

I know for sure that in this village, I can track it down as far as late 1800 something.

My grandmother taught my mother how to bake this bread, and my mother taught me.

In the hot spring rye bread recipe, we have rye, flour, sugar, baking powder, salt, and milk.

We put this in a pot, we put butter in the pot, then we wrap it with plastic foil,

and we put it down in our hot spring hole for 24 hours.

It's very obvious to see if the ground is hot or not.

I never use a thermometer.

If I need to check the heat, I just use this one.

Our biggest challenge is rain.

If it rains a lot, these holes that we are using can cool down,

and if they are not hot enough, obviously the bread doesn't bake completely.

Everybody eats our bread: our visitors, the locals.

Hot spring rye bread has a unique taste that you don't get from ovens.

The texture of this bread is quite special.

It's quite heavy, it's not the typical light bread.

When you show this to travelers that come to Iceland

and you see their faces, they go "Wow!",

then you start to think that this is quite amazing, actually.