A convertible carriage is a type of horse-drawn carriage that has a folding top, allowing it to be converted from an enclosed to an open-air vehicle. Two common types of convertible carriages are the landau and the calash. A landau is a four-wheeled carriage with a folding top and two facing seats. It was originally designed in Germany in the 18th century and was popular among the wealthy. A calash is a two-wheeled carriage with a folding top and one seat. It was developed in France in the 17th century and was used by both the wealthy and the middle class.