The grey-green moss on Illahraun, along the lagoon road

The lava that the Blue Lagoon sits in is Illahraun, and along Bláalónsvegur — the road in — it is covered in the pale grey-green woolly moss that grows only on old Icelandic lava. From the roadside pull-offs the field rolls away in humps and hollows, with the spa's plume of steam behind and the flat Reykjanes horizon beyond. It is the most Icelandic-looking half hour available within five minutes of a car park.

Colour is the reason to shoot it. The moss goes from silver-grey when dry to a saturated yellow-green after rain, and against it a red coat or a white dress separates instantly; overcast light saturates it further, so the grey days most people apologise for are the good ones here. Low sun from the side turns the humps into a relief map of shadow, which is the frame worth waiting for in the four or five hours of winter daylight or the long orange evenings of June.

And the thing that must be said before anyone steps off the road: this moss is decades old and does not recover. A footprint stays visible for years; a group walking into the field leaves a scar. Shoot from the road shoulder, the pull-offs and any marked path only, and place the couple on bare rock or gravel — never on the moss. Any photographer who suggests otherwise is costing the next twenty years of pictures.

Practically: park only in the pull-offs, well off the carriageway, because this road carries constant spa traffic. The ground either side is loose lava, sharp and ankle-turning, so keep to firm footing. And as everywhere on Reykjanes, check the current road and area status before you drive out — access here has changed at short notice in recent years.