It was a 500 seat house that was active as a Broadway house, mostly with a lot of flops, during the 70s and 80s, before it was demolished.
You didn't ask, but there were several small 499+ seat theatres that cropped up during that same time period that served brief lives as Broadway theatres, in addition to the Playhouse/Jack Lawrence. None of them were very successful.
-The Rialto, a former movie theatre, which stood at 42nd and Seventh Avenue, that was the home of Musical Chairs, The World of Sholem Aleichem, A Reel American Hero and Marlowe, among others.
The Reuters Building was built on that location.
- The Century, which was at one time Billy Rose's Diamond Horseshoe, on 46th Street, in the basement of the Paramount Hotel. It housed A Taste of Honey, Waltz of the Stork, and On Golden Pond transferred there from the New Apollo. I think the place still exists in the Paramount, but is sitting unused.
- The 22 Steps/Princess Theatre, a truly odd theatre, that was on 48th Street between Broadway and Seventh Avenues. The Renaissance Hotel is now on that land. That theatre (which had once been the Latin Quarter) housed some spectacular disasters, including Censored Scenes from King Kong, Coquelico, Fearless Frank, and was also home to the Tony-nominated Pump Boys and Dinettes, which ran a little over a year there.
- The Criterion, on 45th Street and Seventh Avenue, which was Roundabout's first Broadway home, prior to moving to the American Airlines. The Criterion had two stages, a Broadway and Off-Broadway space, and before becoming home to Roundabout, had a very checkered life as a commercial Broadway theatre. Starmites is the only thing off hand that I can remember playing there, but I'm sure IBDB will list more... Those spaces are now occupied by Toys 'r Us and Bond 45.
Begin at the beginning and go on till you come to the end: then stop.