What is in this image? Describe it as if you were explaining it to someone from the 15th century.

This drawing depicts a large wheeled carriage, but unlike those drawn by horses, this one moves by its own mysterious means. It has a face with eyes that are closed and a displeased expression, suggesting a sort of spirit or character within. This wondrous carriage is contained within, allowing many people to sit and travel together without the need for beasts to pull it. There are several windows, which knights could liken to arrow slits in a castle, through which occupants can look out. The carriage rides on four round, solid hoops, possibly crafted from some unknown, smooth material that is able to endure the hardness of stone paths without wearing thin. At the top, a small, round orb could be seen as a decorative finial, akin to those that top the staffs of royal banners. This image represents a magical blend of craft and artistry, a device that moves with the precision of a clockwork mechanism, yet carries the charm of a painted tapestry.