  An optical microtrap is realized on a dielectric surface by crossing a
tightly focused laser beam with an horizontal evanescent-wave atom mirror. The
nondissipative trap is loaded with $\sim$$10^5$ cesium atoms through elastic
collisions from a cold reservoir provided by a large-volume optical surface
trap. With an observed 300-fold local increase of the atomic number density
approaching $10^{14}{\rm cm}^{-3}$, unprecedented conditions of cold atoms
close to a surface are realized.
