Real tennis
Real Tennis is the original racquet game.
It is also known as Royal Tennis, Court Tennis (America), and jeu de paume (France). Players generally just call it "tennis", as opposed to "lawn tennis", but this use of language is obscure.
The rules evolved over centuries from those of an earlier game, similar to fives, pelota or handball, played since the 12th century by hitting a ball with the hand against the walls of monasteries. The rules stabilised around 1600. The game was popular among 18th and 19th century aristocrats, but today are only a few dozen courts in the world. This is partly because a real tennis court is a very substantial building (a larger area than a lawn tennis court and with walls and ceiling to contain all but the highest lob shots). In the UK there is something of a revival with new courts being built, for example at Clifton College and the Millenium Tennis Court at Middlesex University. There are currently active clubs in the UK, Australia, the United States and France.
The basic rules and scoring are similar to those of modern lawn tennis, which derives from real tennis. The ball has a core made of cork with fabric tape tightly wound around it and is covered with a hand-sewn layer of felt. It is much heavier and less bouncy than a lawn tennis ball, and nearly as heavy as a cricket ball. The racquets are made of wood and use very tight strings to cope with the heavy ball. A Real Tennis court is enclosed by walls with sloping roofs (known as "penthouses") and buttresses which may all be played off. The service only happens from one end of the court and the ball has to travel along the penthouse to the left of the server. It has extra complexities in that when the ball bounces twice the receiving player does not generally lose the point outright. Instead a "chase" is called and the receiver gets the chance to replay the point from the other end under the obligation of getting every shot to have a second bounce further back from the net than the shot he failed to reach. This feature prevents drop shots and combined with the skill involved means that Real Tennis is an unusual sport in which people reach their prime later in life.