Metric was assigned as a designer of The Crown Property Bureau’s Nakarapirom underground parking garage project located on the Inner Ratanakosin Island adjacent to the Grand Palace, historical center of Bangkok. This 700-car (plus a number of motorcycles and bicycles) garage was designed to be a 3.5-storey building of 29,000-sq.m. floor area, totally underground, hidden from street view by a 10,000-sq.m. garden as roof. The site is attached to Chao-Praya river bank with sand pocket connected to the river, in which, unbalanced lateral pressure and underground water pressure that were expected in both construction period and long-term operation period then becomes an important criteria for structural design. Close to a number of historical buildings, high sensitivity to settlement and vibration was a challenge. Scope of work included development and detailed design considering traffic flow and disabled-friendly environment.  Mechanical work involved air circulation (extra human comfort) and flood protection of the underground of the parking lot. Electrical work covered power supply and distribution, lighting and power outlet, fire alarm and detection, CCTV system (security) and emergency alarm, access control and parking guidance system. Metric also supported piping and drainage of the roof garden. Electrical work concerning power supply and distribution for public event on the roof garden, was in consideration.