We spent today a little differently. We have been chasing landscapes lately, waterfalls, glaciers, and the big empty country of the highlands, but today we did not go out to look at scenery. We went out to learn things. We made three stops, all in the same corner near Hella, and all of them were about people and the earth rather than about a view.

The first was the Caves of Hella, which are a genuine mystery, and nobody can tell you for certain who made them or when. The second was Keldur, an old turf farm that shows how Icelanders actually lived, and how poor this country was until very recently. The third was the Lava Centre, which is about the ground itself, the volcanoes that are still erupting a short drive from where we sat. Three stops in one day, one thread through them. Not what the country looks like, but what it is, and what it has been through.

The weather is keeping us at the campground now, waiting on a ferry to the Westman Islands tomorrow that is not looking promising. So it was a good day to spend indoors and underground, learning.

Our first stop of the day was the Caves of Hella, a set of man-made caves cut into the soft sandstone by the river, right at the edge of the town.

Start with the mystery, because that is the whole reason to come. There are around two hundred of these man-made caves across the south of Iceland, dug by hand into the rock. Nobody knows for certain who made them, or when. That is not a figure of speech. The caves themselves cannot be dated. Rock that has been carved does not carry a date the way a layer of ash or a piece of wood does, so there is nothing in them that science can pin to a year, and nothing that can rule a theory in or out. They sit there, carved and silent, and they do not answer.

The theory that draws people is the one about the papar. In the Book of the Icelanders, written by Ari Þorgilsson around 1120, there is a short passage that says the Norse settlers, arriving in the ninth century, found Christian men already here. The Norse called them papar. They were most likely Irish or Celtic monks. According to Ari, they left, because they did not want to live among heathens, and they left behind Irish books, bells, and croziers. So the oldest Icelandic account of the settlement says plainly that someone was here first, and chose to go.

From that comes the romantic idea: that these caves were dug by those monks, before the Vikings. A few of the caves have crosses and carvings that people point to as support. It is a good story. But it is worth being clear that it is the least likely of the explanations, not the most. Icelanders dug caves like these throughout the settlement and the centuries after it, and used them as sheep shelters, storehouses, and byres. Most of these two hundred caves are almost certainly ordinary farm work, made by the Norse and their descendants over hundreds of years. There is no archaeological proof of Irish monks in Iceland before the Norse, nothing datable, no ruins, no graves. The crosses prove nothing either, since Iceland was Christian from the year 1000, and a cross fits any date after that just as well.

And here is the heart of it. Carved rock cannot be dated. There is no way to tell a cave dug by a monk in 870 from one dug by a farmer in 1300, because the carving itself carries no date and leaves no layer to read. So the caves can neither confirm the monks nor rule out the Vikings. The likeliest answer, plain farm work by Icelanders, and the romantic one, Irish hermits before the settlement, sit side by side, and nothing in the rock can separate them.

We stood in them and did not come away with an answer, which is the correct way to come away. The oldest book says someone was here before the Norse. The caves were most likely dug by the Norse and the Icelanders who followed. Whether any of them go back further than that, to the men Ari wrote about, nobody can yet tell, and the rock is not saying.