Happy 60th birthday to Manhattan’s venerable Paris Theater, which claims to be the oldest continually operated arthouse cinema in the United States. When Marlene Dietrich cut the ribbon to open the theater on September 13, 1948, the city boasted many larger theaters than the 586-seat Paris, which unlike many post-War arthouses (such as the Cinema Studio and the Festival) has incredibly defied demolition despite being on prime real estate just off Fifth Avenue, across 58th Street from the Plaza Hotel. Now the Paris, which still feels comparatively intimate, is actually the second-largest single-screen theater in Manhattan after the 1,100-seat Ziegfeld. According to Cinema Treasures, the Paris has exactly one more seat than the 585-seat AMC Loews 72nd Street 1 (better known by its former name, the Loews Tower East). The only other single-screen commercial venue that I know of is the 240-seat United Artists East 85th Street. In celebration of the birthday, patrons attending today’s five shows of “A Secret” will receive a free bag of popcorn and a soda and will be able to participate in a drawing. Anyone who brings valid proof they were born on Sept. 13, 1948 will receive a pass for two, good for a year.