  Nonergodicity observed in single-particle tracking experiments is usually
modeled by transient trapping rather than spatial disorder. We introduce models
of a particle diffusing in a medium consisting of regions with random sizes and
random diffusivities. The particle is never trapped, but rather performs
continuous Brownian motion with the local diffusion constant. Under simple
assumptions on the distribution of the sizes and diffusivities, we find that
the mean squared displacement displays subdiffusion due to non-ergodicity for
both annealed and quenched disorder. The model is formulated as a walk
continuous in both time and space, similar to the L\'{e}vy walk.
