Here's an odd vessel, the SS Bessemer.
This drawing is sort of a composite from various resources of varying accuracy, the best resources being several photos I found of the ship during it's trial and public voyage, as well as photos of the saloon interior and the saloon test model.
The ship's unique swinging saloon was designed by Sir Bessemer to combat seasickness by keeping the floor of the saloon horizontal while the ship rolls. It achieved this by having the saloon suspended on gimbals and having a steersman control the hydraulics to level the saloon. The ship proved to perform very poorly during its trial and its first (and only) voyage, colliding with the Calais pier twice and ultimately driving away anyone interested in investing in Sir Bessemer's Saloon Ship Company and leading to the demise of both the ship and the company. After she was scrapped in 1879, the saloon continued its existence as a billiard room for the ship's designer, Edward Reed. Reed's house later became a women's college where the saloon was used as a lecture hall until its destruction during the bombings of England in WWII.