When the Ruth J. Simmons Quadrangle reopened in mid-October after a five-month closure, passersby likely noticed the newly dedicated Stephen Sondheim Amphitheater. But behind the fences that surrounded the site during its renovation, most of the project did not involve building the amphitheater itself. Roughly two-thirds of the construction project took place underground, according to Paul Dietel, the assistant vice president for planning, design and construction.