Question: Feinstein's/54 Below is located in the basement of a former nightclub that was originally built as what opera house?

Context paragraphs:
Feinstein's/54 Below: Feinstein's/54 Below is a cabaret and restaurant in New York City owned by Broadway producers Steve Baruch, Richard Frankel, Marc Routh and Tom Viertel.  It has hosted shows by such notable performers as Patti LuPone, Ben Vereen, Marilyn Maye and Barbara Cook.  It is located in the basement of Studio 54.

Tibbits Opera House: Tibbits Opera House is the second-oldest theatre in Michigan, having been built in 1882.  Rich in history and ambiance, even today the theatre offers theatre-goers nearly perfect acoustics, an intimate 499-seat setting, and a fine array of performances throughout the year.  Barton S. Tibbits originally built the opera house with wisdom and vision.  The aim was high art, timeless architecture, excellent acoustics, splendid furnishing and the finest of entertainment.  Tibbits put Coldwater on the map as one of the few small cities in the nation with a social and cultural center of such grandeur.  Thanks to the forward-thinking individuals who saved the opera house from destruction in the 1960s, the citizens of Branch County still have the opportunity to experience the opera house and the cultural activities valued so highly by its early residents.

Metropolitan Opera House (Saint Paul, Minnesota): The Metropolitan Opera House was a historic opera house located in Saint Paul, Minnesota located at 100 East Sixth Street.  Plans to build the house began after the Grand Opera House burned down on January 21, 1889.  Initial plans for the house were designed by Leroy Buffington, but his plans were abandoned due to insufficient funds.  Business tycoon Robert Mannheimer eventually came to the rescue, providing half a million dollars towards the project.  New plans by Charles A. Reed were used for the house which was built over a few months in 1890.  The opera house opened for business that year and served as Saint Paul's opera venue until 1936.

Lexington Opera House: The Lexington Opera House is a theatre located at 401 West Short Street in downtown Lexington, Kentucky.  Built in 1886, the Opera House replaced the former theatre, located on the corner of Main and Broadway, after fire destroyed it in January 1886.  The new Opera House was designed by the renowned architect Oscar Cobb and is listed on the National Register of Historic Places for its historical and architectural significance.  Now owned and operated by the Lexington Center Corporation, the Lexington Opera House is host to ballet, opera, children's productions, family shows, comedy, music and professional national Broadway tours.  The Lexington Opera House is one of the only 14 theatres in the country built before 1900 with less than 1,000 seats that is still in operation as a live performance venue.

Peabody Opera House: The Peabody Opera House (formerly known as the Kiel Opera House) is a civic performing arts building located in St. Louis, Missouri.  Founded as the Kiel Opera House, it opened in 1934 and operated until 1991, when it and the adjacent Kiel Auditorium were closed so the auditorium could be demolished and replaced by the Scottrade Center.  When the auditorium was slated for demolition, the owners of the complex promised to rehabilitate the opera house as well.  The owners, however, never renovated the building, instead claiming that they had fulfilled their financial obligations.  In June 2009, the St. Louis Board of Aldermen voted 25–1 to subsidize the renovation and reopening of the Opera House under the direction of its new owners, Sports Capital Partners.  The subsidies were funded by municipal bonds and state/federal historic tax credits.  On July 12, 2010, it was announced that the name of the opera house would be changed to the Peabody Opera House, named after the company Peabody Energy.  The renovation lasted for fourteen months and included the construction of a new entrance for the building.

Tecumseh Opera House: The Tecumseh Opera House, located at 123 S. Third in Tecumseh, Nebraska, is a historic building built in 1880.  It is a two-part commercial block building, and has also been known as Seaver Bros.  Opera House, as Smith Theatre, as Hahn Opera House, as Spicknall & Goodman Opera House, as Goodman & Canfield Opera House, and as Villars Hall, and it has been denoted NeHBS #J007-53 and OHBIN #ll-29-OI.

Workington Opera House: The Workington Opera House, or "The Opera" as it was known, is a purpose built theatre located in Workington, Cumbria, England.  Originally built as the Queen’s Jubilee Hall & Opera House it was gutted by fire in 1927 and rebuilt with a fine wide auditorium, and Ornamental ceiling with seating for 1200.  The theatre has good sightlines and a large stage and currently sits empty after its former use as a bingo hall ended in 2004.

Studio 54: Studio 54 is a former nightclub and currently a Broadway theatre, located at 254 West 54th Street, between Eighth Avenue and Broadway in Manhattan, New York City.  The building, originally built as the Gallo Opera House, opened in 1927, after which it changed names several times, eventually becoming CBS radio and television Studio 52.

Warren Opera House Block and Hetherington Block: The Warren Opera House Block and Hetherington Block are historic buildings located in Greenfield, Iowa, United States.  They are both 2½-story brick structures.  The Opera House block, originally owned by E.E. Warren, is located on the corner and features a corner turret.  It housed Warren's dry goods store and a theatre.  The adjacent commercial block was originally owned by John J. Heatherington, and is similar in style to the Opera House block.  Both buildings feature facades with a tripartite arrangement and center frontispieces that project slightly forward, a broad rock-faced beltcourse that runs above the second floor windows, a narrow metal cornice, and a brick parapet with finials.  The Opera House's parapet has a triangular pediment with "Opera House" on a rectangular base, and the Hetherington Block has a similar feature in a simplified form.  The buildings were listed together on the National Register of Historic Places in 1979.  In 2014 they were included as a contributing property in the Greenfield Public Square Historic District.

Phoenix Opera House Block: The Phoenix Opera House Block is a historic building in Rushville, Illinois.  Built in 1882, the building housed commercial businesses on the first floor and an opera house on the second floor.  The opera house hosted traveling performers and theater companies as well as local social events.  The opera house closed in 1910, as churches began to host the town's social functions and the local movie theater provided entertainment.  From 1924 to 1956, the opera house served as a Masonic lodge.  The building is one of the few surviving examples of a combined opera house and commercial building.

Supporting paragraphs: Feinstein's/54 Below Studio 54
Answer: Gallo Opera House