  How many copies of a parallelepiped are needed to ensure that for every point
in the parallelepiped a copy of each other point exists, such that the distance
between them equals the distance of the pair of points when the opposite sites
of the parallelepiped are identified? This question is answered in Euclidean
space by constructing the smallest domain that fulfills the above condition. We
also describe how to obtain all primitive cells of a lattice (i.e., closures of
fundamental domains) that realise the smallest number of copies needed and give
them explicitly in 2D and 3D.
