This level has you climbing up and around a pair of tall towers. Early on you can get a Cat Power-Up in this level, which can make thinks a lot easier.
Green Star #1
Not far from where you can get the Cat Power-Up, an Lift rises up to the next floor of the tower. To the left of the elevator is a wall leading to a secret ledge that hides the first Green Star.
Stamp
The Stamp is on a cloud platform that hovers just above the first Green Star. The Cat Power-Up is required to reach it.
Green Star #2
The roof of the tower is guarded by three Magikoopas. Beating them causes the second Green Star to appear. If you still have the Cat Power-Up at this point, try to hold on to it for the later part of the level. After this fight, take the gondola over to the next tower.
After the Checkpoint Flag, you come across a locked Warp Box. You must climb the next tower to retrieve all the Key Coins before you can exit the level.
The Key Coins are not actually hidden, so the climb is not about hunting down well hidden items. You find all five Key Coins as you climb up the tower past enemies that try to slow down your progress.
Green Star #3
Just past the third Key Coin and next to the fourth, you see a set of breakable blocks in the base of the tower wall. Defeat the nearby enemy, then break open the blocks to find a hidden passage with the Green Star.
As soon as you collect the fifth Key Coin, a poison fog starts to flood the tower from the roof. You need to race back down the tower and reach the unlocked Warp Box. If the poison fog hits you, it’ll cost you a life.The Warp Box takes you to the Goal Pole zone, so this is the final stretch!