Super Mario Land 2: 6 Golden Coins/Tree Zone

Tree Zone takes place in a humongous tree, which you will need to scale to reach the boss at the top, a nasty crow called Kurosu. You'll have to face a bunch of enemies just to reach the entrance to the tree, wade through the sticky sap in the tree's interior, scale tree branches that are crawling with ants and even trespass through a beehive just to get to the top. Climbing Tree Zone won't be an easy task, and this zone will prepare you for the challenges you will have to face later.

Traversing the roots
This level is primarily divided into two sections, the surface and the interior of the roots. You will face four new types of enemies in this stage, the toad-like Bopping Toadies, the drill-nosed Ragumo, the giant insectoid Kyotonbos and the peculiar Spikey. All three of them can be defeated with stomps or fireballs, even the spikey, despite its spiked back.

On the first single tile of platform, you can jump into the air to reveal a hidden block. Continue jumping to reveal more hidden blocks until you reach a 1-Up. You can do the same thing at the first raised section of root near the spikey. After the checkpoint bell, you can go beneath the root to get coins and a power-up, but you must return to the surface in order to proceed.

After the highest section of the root around the area with the spikey, you can reveal another series of hidden blocks which lead to a path lined with coins, which also lets you bypass a bit of the level. Go right a bit more and you should reach the end of the level. The bell can be reached by jumping off the block formation.