It’s probably the only picket fence in the Amazon, but scientists have no idea what made it or what its purpose might be.

Georgia Tech doctoral student Troy Alexander stumbled upon these two-centimeter-long white structures growing on trees in Peru on June 7.Since then, the intricate handiwork has baffled scientists. Although most agree it was likely built by an insect, no one can identify the species that built it, or what the fence might be protecting.