This paper presents a study on the electronic properties of a van der Waals heterostructure composed of a monolayer graphene flake and a rotationally-aligned hexagonal boron nitride (hBN) substrate. The interlayer atomic registry results in a local breaking of the carbon sublattice symmetry and the formation of a long-range moiré superlattice potential in graphene. This interplay between short- and long-wavelength effects leads to a band structure with isolated superlattice minibands and a large band gap at charge neutrality, which can be tuned by varying the interlayer alignment. Magnetocapacitance measurements reveal fractional quantum Hall states and integer conductance plateaus at non-integer filling factors, reflecting the massive Dirac dispersion and the emergence of the Hofstadter butterfly in a symmetry-broken Landau level. The ability to engineer the band structure of graphene through the use of hBN as a substrate opens up new possibilities for the design of electronic devices and the study of many-body effects.This paper presents a study on the electronic properties of a van der Waals heterostructure composed of a monolayer graphene flake and a rotationally-aligned hexagonal boron nitride (hBN) substrate. The interlayer atomic registry results in a local breaking of the carbon sublattice symmetry and the formation of a long-range moiré superlattice potential in graphene. This interplay between short- and long-wavelength effects leads to a band structure with isolated superlattice minibands and a large band gap at charge neutrality, which can be tuned by varying the interlayer alignment. Magnetocapacitance measurements reveal fractional quantum Hall states and integer conductance plateaus at non-integer filling factors, reflecting the massive Dirac dispersion and the emergence of the Hofstadter butterfly in a symmetry-broken Landau level. The ability to engineer the band structure of graphene through the use of hBN as a substrate opens up new possibilities for the design of electronic devices and the study of many-body effects.