Abstract
We present an exact quantum-mechanical calculation of the conductance for a large but finite two-dimensional antidot lattice. Rich structure is predicted for the mesoscopic system and is characterized by two kinds of conductance fluctuations: slow fluctuations as seen in the thermally averaged conductance and rapid fluctuations appearing at low temperature on the top of the slow ones. The former are due to electron wave interferences in a form of Bragg reflections, while the latter can be attributed to resonant tunneling via electron states of the system.