The Sealed Grounds is the name of a location in the Blue Dragon anime.
The Sealed Grounds is the place where the 7 Soldiers of Light sealed the Darkness. When all Seven Soldiers of Light are there, a barrier is built. If someone breaks the seal, the darkness will come out.
Some years later, this ended up happening when Zola orchestrates those who are descended from the Seven Soldiers of Light to appear at the Sealed Grounds. While she was busy with General Logi, Zola ended up manipulating Shu into releasing the darkness which started to cover the area.