  A cascade of dihedral symmetries is hidden in Young's lattice of integer
partitions. In fact, for each integer N>2 the Hasse graph of the subposet
consisting of the partitions with maximal hook length strictly less than N has
the dihedral group of order 2N as its symmetry group. Here a new interpretation
of those Hasse graphs is presented, namely as the 1-skeleta of the injective
hulls of certain finite metric spaces.
