“Underground, there are vast areas where rivers of milk flow, but, they are inaccessible to humans while there live on the ground. Those vast areas are linked to some shafts, chasms, and caverns like the Urbion Shaft, the Okina Chasms, the Albi Chasms and the caves in Mounts Anboto, Muru and Txindoki. Certain atmospheric phenomena are originated in those underground regions, mainly the storm clouds and the violent winds. The blue sky is called Ostri. The stars move around in the sky and, when they set on the west, they dive into the “reddish sea” (also called Itxasgorrieta) to follow their course under the ground. So, the sun, who during a part of her course lights the earth’s surface, shines later under that surface. The Sun and the Moon are goddesses, the Earth’s daughters, and they come back to it every day after crossing the Sky. Humans can enjoy the Earth’s surface during the day but, at night, the surface belongs to the spirits and souls of the dead for whom the Moon shines.” J.M. de Barandiaran.
According to the legends of the Basque Country, Lurra (the Earth) is a giant hull, an infinite hull; and the souls of the dead, the god/goddesses and most of the mythological characters live underground.
The Basque cosmology is heard-based. Ama Lurra (the Mother Earth) is the most important goddess and Eguzki Amandrea (the Grandmother Sun) and Ilargi Amandrea (the Grandmother Moon) are her daughters. Every day, they rise from the underground and, after crossing the sky, they return underground. When the Sun is setting on the west, the people of some villages say their farewells: “The Mother Sun returns with her Mother …” (in Elosua, Plaentzi and Arratia).
Mari is the goddess of the herath , the personification of the earth and nature. She also lives underground. According to a tate from Amezketa, she lives for seven years in the Marizulo Cave in mount Txindoki; and, later, she goes back flying in her golden cart to her cave in Mount Anboto. Mari lives underground too and, like Eguzki Amandrea and Ilargi Amandrea, she keeps returning to Ama Lurra after crossing the sky.
In many mythological universes, but particularly in the Indo-European one, storms, lightning, thunder and wind are originated in the sky. The ancient Basque understanding was different: These natural phenomena are produced under the ground, and they emerge from some caves and chasms. The most important goddess and the personification of the Earth, Mari, often produces and sends the storms. The following story about the famous Okina Cave was told to J.M. barandiaran in the village of Onraita (Araba). Usually, a white cloud comes out of the cave but it disappears as soon as the sunbeams touch it. And, in the summer, the torrential downpours and frightening hair which are produced by the storm clouds coming out from the cave.
Some old expressions in the basque language are clear proof of this. When we talk about the Sun, the Moon or the wind, we say “ … atera du” (literally translated “... someone has got it out, instead of the English expressions “ the Sun comes out” or “ the wind blows”) ; expressing in the basque language that someone performs the action of making the wind blow or the Sun come out. When it rains, we say “euria ari du” (literally translated “ someone produces the rain”). Behind all these expressions, it seems to be the mighty power of a god/goddess such as Ama Lurra or Mari. So, that means we can also find some sings of how the basque Mythology is based on the land in certain basque expressions.