High Entia Tomb is a place that Melia goes into to prove that she is worthy to become successor to the emperor. It is accessed from Eryth Sea, but only after progressing to a point in the story.
Story
Shulk has a vision that shows that she is killed by Tyrea. However, Shulk and the rest come to Melia's aid before she is killed. It also houses the High Entia Godfathers.
There is a number of secret passages, some of which can only be later accessed in the game.
Landmarks and Locations
Landmarks GF
Locations GF
Landmarks B1F
Landmarks B2F
Locations B2F