Super Mario Land 2: 6 Golden Coins/Macro Zone

On the top floor of this humongous house lies Ricky, the second golden coin holder. While he should be easy to defeat, the mountain tunnels leading to his residence has mysteriously shrunk you down to the size of a bug. You will need to dive into an anthill, make your way through the house's plumbing system, climb the house's fireplace and conquer the dusty attic to reach Ricky. Size is no excuse for giving up, so go ahead and go for the golden coin!

The anthill
In this level, prepare to face ants, a lot of ants. In addition to the Antotto you might have faced back in Tree Zone, you'll have to face other varieties like Chikuntos with spiked backs, Gorontos that can dig up rocks and chuck them at you, and even Dokanto, which can launch projectiles at you using the cannon strapped to its back. The platforming is going to get harder from here on out, in fact you'll have to face the constant threat of falling into instant-death water and can even get denied from accessing places due to a slight mistake.

There is at least one section where you're forced to go beneath a low wall on a moving platform. While you can make it across without much effort as small mario, you'll need to crouch when passing through, or else you'll fall off the platform and to your demise. The blocks that can only be destroyed by fireballs return in this level, and is even required to access a few secrets. At the area with five question mark blocks, you can go to the lower level, crouching to avoid the spikes, and reach a block that contains a fire flower and a pipe next to it. Do not jump at the pipe while hugging the wall. Doing so will reveal a hidden block that will prevent you from entering unless you become small, but since the pipe entrance needs to be cleared with fireballs, it means you'll have no way to access it. On the other side is a chamber full of coins and question mark blocks. You'll need to ride the last moving platform to reach the bell at the end.

There is a secret exit in this level, one that will open up a devious shortcut and a secret level. If you can't find it yourself, check the spoiler below.

A midair shortcut
A level exists high above the air that can only be reached by skilled spelunkers who have managed to find an entrance to it above an anthill. This stage has forced scrolling and lots of deadly drops, so you'll need to think fast and act faster to avoid getting crushed or falling. If you're quick enough, you can net yourself some rewards. After the staircase of blocks, you can drill kick down the column of breakable blocks to reach a chamber full of coins (you need to do that if you're not small mario anyways, or else you'll be crushed). You can also use fireballs to open up another room and clear the blocks within to get a 1-Up.

If you manage to clear the level, you will open up a shortcut to the final stage of the zone where you can challenge Ricky the rat. You can still go back and clear the other levels if you like.