On a small clearing in the woods, on the grounds of the Springhornhof, a museum of site-specific outdoor sculpture, in Neuenkirchen, Germany, lies an inconspicuous-looking boulder. There are no signs on the stone or plaques nearby to draw your attention, but you may notice that one end of the rock is covered in black soot. Someone has been trying to light it on fire. But why?

The 1.5-ton boulder is actually a work of art called “Keepalive” by Aram Bartholl. It’s a real boulder, alright, but modified to hide a Wi-Fi router inside that is powered by a thermoelectric generator which converts heat directly into electricity. Visitors are invited to make a fire next to the boulder to power up the router in the stone. Once the router is up and transmitting, visitors can connect to it with their smartphone and browse or download a collection of PDF survival guides ranging from the useless to the bizarre.