We report Submillimeter Array observations of CO (J = 2-1, 3-2, and 6-5) and its isotopologues (13CO J = 2-1, C18O J = 2-1, and C17O J = 3-2) in the disk around the Herbig Ae star HD 163296 at ~2'' (250 AU) resolution, and interpret these data in the framework of a model that constrains the radial and vertical location of the line emission regions. First, we develop a physically self-consistent accretion disk model with an exponentially tapered edge that matches the spectral energy distribution and spatially resolved millimeter dust continuum emission. Then, we refine the vertical structure of the model using wide range of excitation conditions sampled
