Gunnuhver steam vents

Gunnuhver sits at the south-western end of Reykjanes, a hillside of clay stained orange, grey and rust by acid steam, with Iceland's biggest mud pot bubbling at twenty metres across. The whole field breathes: vents roar, steam rolls downhill in sheets, and on a cold still morning a person twenty paces away becomes a silhouette.

That steam is the picture. Position the couple so the vents are behind and slightly to one side, then shoot into the light — backlit steam turns into a wall of luminous white and the figures separate as clean shapes. Wind decides everything: watch which way the plume is running and put yourself upwind, or you will spend the session wiping the front element and everyone will be soaked in sulphurous condensation.

Boardwalks and gravel platforms are the only permitted ground here, and that is not bureaucratic caution — the crust over boiling water is thinner than it looks, the ground moves between visits, and parts of the site have been rebuilt and closed after the ground shifted. Stay on the walkways, keep to the marked viewing decks and treat every rope as final.

Come early or late; the coach tours pass through in the middle of the day between the lighthouse and the Blue Lagoon. Cold weather thickens the steam, so winter out-photographs summer here. And the smell of hydrogen sulphide gets into hair and wool — worth warning clients before, not after.