The boulder is titled Keepalive, and if you heat it up with an open fire, it sends survival tips to a smartphone, tablet or laptop.

Berlin - The tourist won't find this mysterious artwork unaided - it's somewhere among the fields and woods in northern Germany’s Lueneburg Heath - and it's best to have the art-show curator drive you 7km to it by car.

“We are a museum without walls,” says Bettina von Dziembowski, artistic director of Springhornhof, an art gallery in the remote tiny town of Neuenkirchen, Germany. From there, she drives through secluded country lanes.

“We present sculptures and installations in open landscapes,” she explains. There have been around 40 so far, the first ones appearing in 1967.

Chasing down this work - a rock - is not for the casual tourist. You need to be hardcore obsessed with conceptual art. The art gallery will rent you a bicycle to go out and see it.

Not far from the hamlet of Hartboehn - past a small field, a stream and there it is: a granite boulder left here since the Ice Age, a good metre wide, with one side blackened by soot. Leaning against the rock is a small log fire.

Aram Bartholl himself started the fire just before we arrived. The 43-year-old conceptual artist was born in Bremen and lives in Berlin. The rock is his artistic creation - or at least, what’s drilled inside it is.

The boulder is titled Keepalive, and if you heat it up with an open fire, it sends survival tips to a smartphone, tablet or laptop.

“It’s about the combination of fire as man’s first technology, and modern access to data,” Bartholl explains. “The theme is a mix of surviving in nature on the one hand, and in everyday life in the digital age on the other.”

The big rock has been turned into a data storage medium, Bartholl explains.

“The point is to recognise how reliant we are on online services,” he says.

And indeed, a WiFi network suddenly appears on the smartphone’s display. The screen reads “Keepalive” in large lettering, followed by a long list of texts and books - almost 300 so far, with more planned.

“You can also bring files and leave them here,” says Bartholl, whose work has also been exhibited in the New York’s Museum of Modern Art. He is just giving the stone, which was set up in summer 2015, an update and is installing new parts.

The files can only be received in this isolated way - the WiFi only transmits locally.

“It’s not connected to the World Wide Web,” explains Bartholl, who has just returned from a period of teaching in Los Angeles.

“Whoever comes here has also ventured outside of the digitally controlled space,” he explains. “I make conceptual art, art using and about the internet,” as he describes his major theme.

The rock’s digital library includes classic survival strategies in nature, but also those of the digital age.

“In the Internet age, we use the term survival in a completely different way,” Bartholl says. “It’s no longer about surviving in the forest. It’s more like: help, my child is using Snapchat!”

So Keepalive can also offer advice to concerned parents on their offspring’s use of modern messaging.

The spectrum of survival tips ranges from protecting yourself from freezing cold to surving a nuclear war. But you can also find advice on the problems of everyday life. For instance, there are tips on removing stains, DIY divorces, how to deal with a mean boss, and assembling a kitchen from a Swedish furniture store.

There are also instructions for conducting affairs and other erotic encounters, even for those with more exotic tastes.

Those looking to experience their own Stone Age on the Lueneburg Heath should take matches and not be in a hurry - since the fire has to be lit first.

“It takes around a quarter of an hour - the wind and weather have to play along,” says Bartholl.