Third Course (Gold Classics Pack)
From the Super Mario Wiki
This level is highly based on World 1-4 of Super Mario Bros.. In the start of this level, a red pipe leads to a place that is almost exactly World 1-1 of New Super Mario Bros. 2, including the hidden underground area, except that most of the Brick Blocks are replaced with Gold Blocks.
Bowser is fought at the end of this level. After he is defeated, three platforms appear, similar to the New Super Mario Bros. 2 final battle entrance. However, they lead Mario to an area with a Dash Mario level background, a checkered floor and a "THANK YOU!!" message made of coins, followed by a big coin Roulette Block and the Goal Pole.