As I mentioned in an earlier description, the Ethiopian Christian Orthodox Monastery of Na’akuto La’ab near Lalibela, Ethiopia, nestles under a thick ledge of overhanging rock. A mountain - not yet deforested - rises above the monastery, and a deep valley falls away below the monastery's niche. In other words, the monastery lies within a natural watershed.

So, it's not entirely surprising that water drips through the rock ledge that forms the ceiling of the shallow cave in which the monastery was built.

What's utterly astonishing is that much of the floor space in the Church of the Monastery of Na’akuto La’ab is given over to a basin filled with rock bowls placed under drips in the church ceiling.

I searched the Web extensively, and wasn't able to learn much about this amazing feature other than the water collected there is used as holy water.

This is a close-up shot of one of the stone collection bowls. I took the photo in natural light, then processed it gently to bring out the details and the colors. Algae and minerals have combined to produce surfaces of astonishing beauty.

I think the water that falls from the ceiling is laden with minerals, and over the years these basins have been in place (decades? centuries? millenia?), the minerals in the water built up around the edges of the basins, helping define their shapes.   

For example, the material forming basin's oval opening, which overhangs the surface of the collected water, was probably formed by the mineral residue from millions or billions of drops of water.