The Trocadero hosts many of Philadelphia's alternative concerts and events. It is a gorgeous building that dates back to the Victorian era. Listed in the historic register, it is the only 19th century Victorian theatres still in operation in the United States. The Trocadero has served as a Vaudeville hall, cinema and nightclub during it's long life.
The interior features two floors. The ground floor has the large dance floor and the upstairs has the bar and seating. This complicates matters a bit for those who drink and dance, as they will be navigating between the two floors often. The stairs at the Trocadero are narrow and steep. You should take caution when choosing footwear for the night, as many people (this writer included) have taken a tumble on them!
Feel free to dress to the nines when attending an event. The staff at the Troc (as it's affectionately known) are very tolerant of all manner of dress and style - as the Troc has played host to punk, goth, gay, and disco crowds depending on the night.
The Trocadero is currently alternating live acts and local event nights with a movie night (Monday). The schedule can be found on the website, along with ticket prices and directions.