Quoting from this terrific biography:
Napier at first suggested that the Winter Garden’s proscenium be removed, but practicality dictated otherwise, so instead he extended the stage by twenty-four feet, out over the orchestra pit, and wrapped seats around both sides of the extension. The proscenium arch also necessitated changing the shows penultimate scene. In London, Grizabella had made her heavenly exit up a grand staircase that emerged from the New London’s back wall, but in New York her apotheosis had to take place center stage, that the whole audience might see it. The stairway had to emerge, miraculously, from the ceiling, so the technical coordinators, Peter Feller and Arthur Siccardi, broke through the Winter Garden’s ceiling, built a shed to house the mechanism that would operate the stairs and then rebuilt and reinforced the roof.
Indeed, safety first was the production motto, reinforced by the strict New York City fire codes. Everything was fire tested until it surpassed the city standard several times over. Engineers were called in to tell the producers where it would be safe to suspend the lights and false ceiling, which together weighed more than ten tons. A new sprinkler system was installed, and fire walls rebuilt. The theater’s granite foundation was drilled to install the panto spring-trap that would shoot Alonzo the Rumpus Cat up through the floor, and hydraulics were installed to operate both the folding upstage wall (four tons), which dropped down for “Growltiger’s Last Stand,” and the levitating truck tire, which conducts Grizabella twelve feet above the stage floor and twenty-five feet downstage to meet her stairway to paradise.
…
The lighting plan of David Hersey … called for four thousand festoon bulbs, a fiber-optic system in the ceiling to create the illusion of a vast, starry night, and three hundred pairs of blinking cat’ eyes. At center stage was a huge ring of lights that, as the show began, slowly rose into the air like the mothership from Steven Spielberg’s "Close Encounters of the Third Kind" or, Spielberg’s hit that year, "E.T.".
