This is the single most important room in the entire ship. It serves as the meeting room, lounge, and helm for the entire crew. Here the crew can do a number of things. Since the kitchen is located here, they can enjoy a meal here made by Sanji. And because of its comfortable atmosphere, it is the perfect place where the crew can also hold meetings here and discuss what to do next.
The device for steering the ship is also located here. However, unlike regular ships that commonly have a steering wheel, the Going Merry doesn't have one. Instead it uses a "steering pole" with a sheep's head like the one used for the ship's figurehead. By tilting the pole left or right, the rudder at the stern will move in that direction.