In Super Mario 64, what is the name of the first course you enter?

In Super Mario 64, the first course you enter is Bob-omb Battlefield. It is Course 1, reached through the first painting on the upper floor of Princess Peach’s castle after Mario begins exploring the castle grounds.

Bob-omb Battlefield introduces the game’s core 3D platforming ideas: running across open terrain, climbing, swimming, jumping between moving platforms, and collecting Power Stars. Its main landmark is the mountain at the centre of the course, where the Big Bob-omb waits for the first mission’s boss encounter. The course also contains a Chain Chomp, floating islands, a cannon, and several routes that become easier to use as Mario gains access to cannons and new abilities.

Players sometimes confuse Bob-omb Battlefield with the castle itself, which is the hub area rather than a course. Jolly Roger Bay, Cool, Cool Mountain, and Whomp’s Fortress are also early courses, but each is entered after Bob-omb Battlefield. The course’s open design was an important early demonstration of how Mario’s movement and exploration could work in three dimensions.