Sand volcano castle tetrahedral modular

The tetrahedron is the first three-dimensional geometric shape with 4 vertices, 6 edges equal, 4 faces composed of equilateral triangles.
Also called three-dimensional regular simplex, from the formula n-dimensions + 1.

Einstein and the tetrahedron:
At a conference of physicists, overwhelmed by criticism for his preposterous idea of a four-dimensional space-time, he proposed the following problem:

"About 6 toothpicks, build 4 equilateral triangles."

None of those present could be p