The Met was located in the Metropolitan Opera House.
From Curbed Philadelphia:
The Philadelphia Metropolitan Opera House was built in 1908 by Oscar Hammerstein I, the grandfather of Oscar Hammerstein II. Designed by architect William H. McElfatrick, it sat some 4,000 people, becoming the largest theater of its kind in the world. After some time Hammerstein I fell into debt and sold the property, which then went through a number of owners. Over the years it’s served as a movie theater, circus venue, ballroom, and most recently, a church.