  The electronic structure of a crystalline solid is largely determined by its
lattice structure. Recent advances in van der Waals solids, artificial crystals
with controlled stacking of two-dimensional (2D) atomic films, have enabled the
creation of materials with novel electronic structures. In particular, stacking
graphene on hexagonal boron nitride (hBN) introduces moir\'e superlattice that
fundamentally modifies graphene's band structure and gives rise to secondary
Dirac points (SDPs). Here we find that the formation of a moir\'e superlattice
in graphene on hBN yields new, unexpected consequences: a set of tertiary Dirac
points (TDPs) emerge, which give rise to additional sets of Landau levels when
the sample is subjected to an external magnetic field. Our observations hint at
the formation of a hidden Kekul\'e superstructure on top of the moir\'e
superlattice under appropriate carrier doping and magnetic fields.
