We describe the fabrication, characterisation and possible applications of a new type of optical material - a 2-dimensional photonic crystal made of silica and air. This macroporous silica, which is made using the technology of optical fibre fabrication, has properties which differ remarkably from those of conventional materials. We describe how such a material can be used to form waveguides with new and unusual properties, and present some results to illustrate this. Such photonic crystal waveguides could be significant in the design of new lasers and amplifiers.