The location closer to the camera. Go up the stairs and head left - there you have to blow up five mithril bricks blocking your way. Afterwards build stairs form the received pieces, climb them and collect the treasure.
You need to obtain and connect two elements:
#1 - A stick which can be found in the background location, after jumping from the first pillar.
#2 - A flag which can be obtained after the second climb with Gollum, pushing down the pillar and placing a plant. It's in the background and can be reached by going along the wall fragments.
Hand over the complete flag to the nearby soldier.
Treasure: Bubble Pipe
The location closer to the camera. After completing the pillar puzzle and defeating the first group of Orcs, on the ground floor you will see a gate built of LEGO Morgul bricks. Destroy it, head inside the cellar and pick up the chest. To get out, you will have to build a ladder from the pieces lying on the ground.
The location in the background. As you're climbing the tower, you will see a Minikit behind the window. Just do a precise jump from the platform with the sword onto the edge of the building (above screenshot), go round the building and pick it up.
In the place where you found the sword. Just jump up using the laves and grab onto the rope hanging from the bell to obtain the Minikit.
Design: Mithril Boxing Gloves
Right after freeing Gollum, below the stairs on the right you will find a dark room. Head inside to obtain the Design.
Treasure: Statue Hat
Needed: axe, magic
In the area where you defeated the Nazgul for the first time there's a cracked tile. Break it with Gimli's axe. Destroy all chests below but three which you have to properly arrange using Gandalf's magic. In return you will receive the treasure.
After the fight with the Nazgul you have to jump through the breach in the wall and head further to the right. The chest will fall into your hands on its own.
After the second Nazgul fight, build a ladder, climb it and head left. You should a mithril brick - destroy the with a bomb and jump to the chest.
Head towards the camera - you should find a water tower which you can use to extinguish the nearby fire. Now just pick up the Minikit.
You need to destroy five water wheels. Three can be found in the first area of Isengard, one in the second (after crossing the bridge) right before the wall of fire and the last one to the left of the dam.
This time you have to destroy three fragments of Saruman's tower using the rocks. Two pieces can be hit from the beginning location, while the third after crossing the bridge.
After getting through the wall of fire you will find a small fire with the chest inside. Once again extinguish it with the water tower.
As you're moving towards the dam, on the right you will see train rails and at the very top a car. You need to clear a path for it by throwing rocks at the stones blocking the rails. When the car reached the very bottom, a Minikit will fall out of it.