The petroglyphs date back to the 4th Century AD, about the same time as the first calendar. Today, we can admire the petroglyphs because of the quality of the rocks on which they were carved. To express their beliefs, the native artists carved the rocks using flint and obsidian chisels.
The petroglyphs show that the Chorotegas and Niquiranos* had a highly organized and advanced culture. Many studies have interpreted the petroglyphs as religious symbols with the shapes indicating specific relationships: geometric-celestial bodies; anthropomorphic and zoomorphic-gods; circles and spirals-eternity and the human passage to another dimension. You can admire several petroglyphs in San José de san Marcos where you can find a representation of a eagle with opened wings.
On the San Antonio farm, a strip of land juts into the Cocibolca Lake, there are many petroglyphs with circular, spiral, square and rectangualr shape. In the Siloé Evangelic temple of Altagracia, a blok toward east, house there is a stone engraved with an "X" and cross shapes. This stone was used by the natives for
According to Dr Davila Davila Bolaños, these were the characteristic symbols of the sun's cult stones: Tagüizapa and San Silvestre are among the most important archaeological sites on the island of Opetepe. Four idols have been found on these sites and many more may be buried.
On the La Primavera farm, at the mouth of the Rio Buen Suceso, there are many petroglyphs of different styles. In the Madera volcano, in the neighbourhood of the Cigüeñ?; there is the Cross of the South painted in a mediumsize rock and nearby, there are many sculptures of prehistoric animals.