This study of thermal convection uses the following geometry: a horizontal layer of fluid heated from below and cooled from above, with a periodic array of evenly spaced square cylinders occupying the center of the layer. Periodic boundary conditions are employed in the horizontal direction to allow for lateral freedom for the convection cells. A two-dimensional solution for unsteady natural convection is obtained, using an accurate and efficient Chebyshev spectral multi-domain methodology. Here for selected Rayleigh numbers we systematically increase the width to height of the computational geometry from one to two to three and so on up to twelve. Results will be presented for only the case of adiabatic internal bodies and in all the cases periodic later boundary condition is enforced. It is thus clear that the size of the domain plays an important role in dictating the nature of convection and the resulting time history of Nusselt number. Furthermore, it is clear that the system prefers wide aspect ratio convection cells which can only be accommodated in sufficiently large computational domains. Convergence appears to be slow and based on present results it can be conjectured that a much wider domain of aspect ratio of the order of 20 or so will be required to fully approach geometric convergence.