The plan of the Casino is in the shape of a Greek cross, and is only fifty feet square. There are three floors containing sixteen rooms. Although small, they are entirely habitable, with service rooms in the basement, reception rooms on the main floor, and sleeping quarters on the upper floor. There is, however, no evidence of any long term occupation of the building. The exterior of the building is that of a one-room Greek temple, so the complexity of the interior was achieved by remarkable architectural design. This includes faux windows, gib doors, hollow columns, and disguised chimneys. Only half of the great front door actually swings open to admit entrance.
Very little is known about how the inside of the building originally looked. There are brief descriptions surviving in Charlemont’s own correspondence or in that of visitors, or rare mentions in sales catalogues. The exterior of the building is heavily decorated. Four statues adorn the attic storey; Bacchus, Ceres, Venus, and Apollo declare the abundance and love of good living that inspired the creation of the Casino. Around the chimney-urns curve mermaids and mermen. The ‘ceilings’ of the outside porches are densely carved to create a stucco effect. Four large Egyptian-style lions guard the corners.
William Chambers was the architect who designed the Casino. Born in Sweden to a Scottish father in 1723, he spent the first few years of his working life travelling to and from China as an agent of the Swedish East India Company. At the age of twenty-six, he began training as an architect in Paris, later living in Rome, where he was a member of Charlemont’s circle. He moved to London to establish his practice in the same year that Charlemont returned to Dublin (1755). He achieved great success in England, with much employment from King George III and his mother, the Dowager Princess Augusta. His Treatise on Civil Architecture, published in 1759, was a huge influence on Palladian neoclassicism in Britain. The Casino appeared in this Treatise as a plate illustration (image below). Chambers would go on to count James Gandon as one of his students.
As well as the Casino at Marino, Chambers completed designs for Charlemont House and Trinity College, and for modifications to Rathfarnham Castle, Castletown House, and Leinster House, among others. He never, however, visited Ireland in person. His projects with Charlemont were discussed at great length, over two decades, in numerous letters; many of these can be read today in the Royal Irish Academy. One of his original drawings for the Casino is on display in the building.