Ancient Roman ruins at Pompeii have been fitted with invisible solar panels, in a move that will ensure the archaeological site’s sustainability and cut costs. The innovative panels, which blend into the background by imitating traditional materials, were installed on the House of Cerere, on a thermopolium—a Roman snack bar—and on the House of the Vettii, which recently reopened following 20 years of restoration work.

“They look exactly like the terracotta tiles used by the Romans, but they produce the electricity that we need to light the frescoes,” says Gabriel Zuchtriegel, the director of the archaeological park of Pompeii, in a press release.

Three-and-a-half million tourists annually explore the vast ruins of the ancient Roman city, which was buri