Map Stones are statues that you can find in each area of the game. Once you've found them, stand in front and activate it to reveal all the collectibles and hidden stuff around the area. Bring up the map, select the desired area, then follow the guide below on where you can find each map stone in an area.
Hobbiton - From Frodo's house, go down the hill and cross the bridge.
Bree - Enter Bree, go to your right, it is beside a fence.
Weathertop - When following the path to the Weathertop chapter, you will see it located below the hill.
Rivendell - Below the stairs that you will follow in the main story interlude.
Mines of Moria - Left of the entrance to the Mines of Moria.
Lothlorien - Near the boats at the river, at the stairs which leads to Lothlorien.
Amon Hen - On the trail in the middle of the hills.
Emyn Muil - After the Amon Hen level, before starting the Taming Gollum level.
Dead Marshes - On the center island in the swamps.
Edoras - At the left of the stairs which leads to the golden hall.
Helm's Deep - Left of the trail to the entrance of Helm's Deep.
Cirith Ungol - At the bottom of the incline leading to the fortification.
Isengard - Near the door into Isengard.
Minas Tirith - Located close to the White Tree above the area.
The Black Gate - Right side of the Black gate.
Minas Morgul - Near the watery area at the eastern part of the place.