The Yellowstone National Park of Iceland is near Lake Mývatn (lake of MIDGES) in the North, an area of active volcanism.
Like Yellowstone, this area could blow up any time.
There are a dozen great day hikes to choose from. You could link them together – I met a British couple doing this – or drive trailhead to trailhead, as I did.
A short walk from the Information Centre is Hverfjall.
This one last erupted 2500 years ago. Whew.
It’s an easy walk up and around the rim. Weather permitting.
besthike.com 
Great images. Nothing like anything I have ever hiked yet!
DSD
That is one epic looking crater!