Scattered across Ometepe, especially on the slopes of Maderas, are hundreds of pre-Columbian petroglyphs — spirals, faces, sun discs and stylised animals carved into volcanic boulders. They were made by the island's pre-Hispanic inhabitants between roughly 300 BC and 1500 AD, who called the place Ometepetl ("two mountains") in Nahuatl. The largest concentrations are around Magdalena, El Porvenir and the trail up to the Maderas crater lake.
Many of the panels still sit where their makers carved them, in cattle pasture and coffee plots, and reaching them often involves a short scramble. Most homestays on the island can arrange a local guide to walk you between sites and point out motifs you would otherwise miss. The petroglyphs are unprotected and unstaffed, so behave like a guest: do not touch the carvings and do not chalk or wet them for photographs.