Significant both for its important role in the care of the mentally ill and for the unusually high quality of its architecture, the landmark Worcester State Hospital  Clock Tower was built in 1877.   The centerpiece of what was then known as Worcester State Lunatic Hospital; its soaring iconic tower rises 250 feet above Lake Quinsigamond and can be seen for miles around.  Designed by Boston architects Weston & Rand in the High Victorian Gothic style, it served as the administration building for a 600-bed hospital designed for the humane treatment of the mentally ill and built on the popular Kirkbride plan.  The Hooper Turret, a circular structure that is now free-standing, was added to the complex in one of several 19^th-century enlargements.  Both buildings are made of ferruginous gneiss rubble, quarried from nearby land, and trimmed with red brick and rock-faced granite.