A replica of the Eleanor, one of the ships involved in the Boston Tea Party in 1773, a protest of a tax imposed on the American colonies by the British government. It's part of a museum in Boston Harbor. Patrons can throw crates of tea over the side, which are then pulled back onboard for the next group of tourists to toss.
"How do you know I'm mad?" said Alice.
"You must be," said the Cat, "or you wouldn't have come here."