Where is the fourth heart pillar on super paper Mario Wii?

First, make sure you have Thudley, the one that looks like a weight. Go on the second floor where merlon's house is located and flip to go to the outskirts. From there you will see five of these things that look like the ones you saw in the ocean on the way to fort francis. hit them all up with thudley, then flip and there will be an arrow on each one saying if it goes up or down. Hit them up or down accordingly and a heart pillar will apear.