Recycled sets?

Most of the (interior) sets looked pretty solid and detailed. Is this all really Daniel Haller's talent for re-dressing virtually anything to look good, or was he abetted by standing sets left over from another bigger-budgeted film? Everything else about the film, including the supporting cast, the library music and the stock footage battle montage, is so cheap they couldn't possibly afford to build all those sets. Does anyone know?