In the days of the Nahuatls, Volcán Maderas  was called Coatlán, “the place where the sun lives,” and Concepción was known as Choncoteciguatepe, “the brother of the moon,” or Mestliltepe, “the peak that menstruates.”
In the lush forests of the lower slopes of the two volcanoes, the Nahuatls performed complicated rituals in honor of many different gods: Catligüe, the goddess of fertility; Ecatl, the god of air; Migtanteot, the god of death; Tlaloc, the god of soil; and Xochipillo, the goddess of happiness
The Nahuatl gods were all-powerful and vindictive, and spent their days in the land where the sun rises doing what all-powerful gods do best — feeding on human blood.
The concept of a soul was an important part of the Nahuatl belief system, as were the concepts of an afterlife and some form of reincarnation. Their calendar consisted of 18 months of 20 days each, for a total of a 360-day calendar year.
They believed in a cycle of catastrophic events that recurred every 52 years, and according to that cycle the Nahuatls would store grains and water, in case this were the year.
Scattered around the island of Ometepe , but principally on the north and northeastern slopes of Volcán Maderas , are the statues and petroglyphs, carved around the year A.D. 300, that paid homage to the Nahuatl gods. Spirals are a consistent theme, representing perhaps calendars or the Nahuatl concept of time and space. It has been suggested the spirals may also represent the islands themselves, or that the twin-spiral shape of Ometepe gave the island even more significance to the islanders, as it fit in with their ideas about the cosmos.
More mundane images can also be identified in the carved rocks: monkeys, humans hunting deer, and a couple in coitus, suggesting Nahuatl wishes for prosperity and fertility, or just a bit of monkey business.