  Artificial spin ice is a frustrated magnetic two-dimensional nano-material,
recently employed to study variety of tailor-designed unusual collective
behaviours. Recently proposed extensions to three dimensions are based on
self-assembly techniques and allow little control over geometry and disorder.
We present a viable design for the realization of a three-dimensional
artificial spin ice with the same level of precision and control allowed by
lithographic nano-fabrication of the popular two-dimensional case. Our geometry
is based on layering already available two-dimensional artificial spin ice and
leads to an arrangement of ice-rule-frustrated units which is topologically
equivalent to that of the tetrahedra in a pyrochlore lattice. Consequently, we
show, it exhibits a genuine ice phase and its excitations are, as in natural
spin ice materials, magnetic monopoles interacting via Coulomb law.
