The Taj Mahal complex is bounded on three sides by crenellated red sandstone walls, with the river-facing side left open. Outside the walls are several additional mausoleums. The main gateway (darwaza) is a monumental structure. The face is a grand recessed arch (iwan) set within a rectangular frame and flanked by alcoves in two storeys, like the facade of the Taj Mahal. Its pishtaq arches also incorporate the calligraphy that decorates the tomb. It utilizes bas-relief and pietra dura inlaid decorations with floral motifs. The vaulted ceilings and walls have elaborate geometric designs, like those found in the other sandstone buildings of the complex. The plinth and tomb took roughly 12 years to complete. The remaining parts of the complex took an additional 10 years and were completed in order of minarets, mosque and jawab, and gateway.