The Ambassador holds the honour of being Dublin's longest-running cinema, and was operational on and off until 1999. It is now a music venue.

The building was constructed as part of the Rotunda Hospital in 1764 as an assembly hall and social rooms. It was primarily used for vital fundraising events for the adjacent hospital, and was therefore called the Rotunda.

From 1897 onwards, the venue was given the name Rotund Room and played host to a number of 'moving picture' screenings, which at the time were somewhat of a novelty. From about 1908 onwards it was used more regularly to show film presentations and in 1910 it became a full-time cinema, with 736 seats, a basic layout at the time. Again known as the Rotunda (it's nickname being the 'Roto' or the 'Roxy'), the cinema-going public thronged to the venue. Over the years the cinema changed hands, until the 1940s when it was run by Capitol and Allied Theatres Ltd.

In the 1950s the cinema was redesigned, increasing the capacity to 1,200. Added to the main hall was a balcony (containing 500 seats) with private boxes. A new entrance area was also constructed. The cinema was re-opened on 23 September 1954 as the Ambassador. It became a gala event venue, holding screenings of many films for the first time.

Of note was the screening of The Blue Max in 1966, which was shot in Ireland. For the screening, a World War 1 plane adorned the roof of the cinema above the entrance.

In 1977 the cinema was forced to close briefly, however reopened during the summer under new ownership. The Green Group ran the cinema until 1988, and the cinema mainly played children's films such as The Care Bears Movie and it's sequels. In 1988, with single-screen cinemas on the wane, it closed.

However, in 1994 it was given a new lease of life when reopened under the ownership of Ward Anderson. Notable screenings upon reopening included Titanic, however attendances were poor, most notably when a reissue of the 1935 film The Informer was screened to as few as two people per show. On 27 September 1999, after 45 years, the cinema closed.

This however wasn't the end of the venue. Entertainment promoters MCD Productions leased the building and it now hosts a variety of events including theatre productions and concerts, all of which use extensive amplification.