Third deck, also known as the upper deck or top tier, is a term used to describe the third level of a multi-story structure or a stadium. Other synonyms for third deck include mezzanine, balcony, gallery, loft, platform, terrace, and penthouse. These terms can be used interchangeably to describe the third level of a building or area where people can gather to watch a performance or sporting event. Whether it's the mezzanine level in a theater or the penthouse suite in a stadium, the third deck is typically a premium seating area that offers a great view of the action below.