South of 4-5: Spike’s Lost City, there is a green pipe on the overworld. Enter this pipe to find a cave, where you will also find a Fire Bro on the map. While not a true Blockade like the other enemy encounters, this one does also hold a Green Star, so those looking to 100% the game will want to do the battle.
Upon starting the battle, you will notice that you only have 100 seconds to complete the course. Your objective is simple, as you need to defeat three Fire Bros, which are enemies you’ve encountered before in the game. They only shoot fireballs, then will jump to a new location and do the same thing. A ranged power-up, like a Fire Flower, will make short work of them, although they shouldn’t put up any kind of trouble at all. After defeating all three, the Green Star will spawn, so grab it to finish.