The lyotropic L-3 phase was used as a template to form nanoporous monolithic silicates with continuously adjustable pore sizes. The monolith was optically isotropic and transparent with a nonperiodic network. The pore size was adjusted by a change in the solvent volume fraction rather than by a change of the surfactant. Unlike other silicates, the bicontinuous pores were water-filled; removal of surfactant was not necessary to access the pores. Measured characteristic dimensions were from six to more than 35 nanometers. For a given solvent fraction, x-ray scattering indicated little variation of pore widths, in marked contrast to the polydisperse pores of aerogels.