We have fabricated a two-dimensional photonic band structure based on macroporous silicon with a gap common to both polarizations and centered at 5 μm. A triangular lattice of circular air rods with a lattice constant of 2.3 μm was etched 75 μm deep in an n-type silicon substrate by electrochemical pore formation in hydrofluoric acid. The porous layer was then micromechanically structured in such a way that 200 μm thick free-standing bars of porous material were left over on the silicon substrate. These bars were then used for measuring the transmission of the photonic lattice. The results showed an excellent agreement with the theoretically calculated structure.