Lindwurm

Lindwurm (リンドヴルム) is the Sacred Land, which located within the Midgar Kingdom and is the place where the demon Diablos's left arm was sealed in the Sanctuary protected by hero Olivier which was controlled by the Nelson Sect faction territory.

History
Lindwurm is a famous city which is one of the holy sites of the most widespread religion of this world, the Divine Teachings. It is a monotheistic religion that believes in the Goddess Beatrix, the one who granted powers to heroes in the legends and that she’s the one true deity.

Once a year, there is a battle event in Lindwurm called the "Goddess's Trial" on the day when the door to the Sanctuary are opens where the challengers must come to fight a memories of ancient warriors that are awoken from within by answering their call. Any challengers who applies in advance can participate, but there’s no guarantee an ancient warrior will answer their call as they are slightly stronger than the challenger for to prove their worth.

When a warrior's strength exceeds a certain level, a warrior spirit matching that level is summoned and fights against that warrior spirit. If the ability is low, it will not be summoned in the first place and will be left as it is. If a warrior spirit is summoned, it will be blocked by a barrier and become a one-on-one battle, and cannot come out until the battle is over.

In the past, there have been cases of being killed by warrior spirits. If anyone defeat the warrior spirit, they will be awarded a medal, which can be effectively used as proof of their ability when joining a Knight Order.

Background
In the past, Olivier cut off Diablos' left arm and then sealed it into the Sanctuary in Lindwurm by the Cult of Diablos. Nelson and his colleagues conducted research to create a drug that could grant immortality called the Tears of Diablos. However, the effect it gave could only delay aging for one year and the amount produced was only the 12 pills that were each year given out by the "Knights of Rounds".

The Cult are make a battle event in Lindwurm called the "Goddess's Trial" when they open the door to the Sanctuary every once a year where all challengers from the world come to fight against the memories of ancient warriors. There are several hundred challengers enter each year, but only about ten end up actually getting to fight as usually the ancient warrior is a little stronger than the challenger and they might not necessarily respond the challengers call.

Ten years ago, the "Wandering Swordsman" Venom managed to summon Olivier, but he lost to him. At some point after that, Venom become Nelson's subordinate and joined the Cult as their "Executioner".

Location
Lindwurm is relatively close and to get there from Midgar Academy to the Sacred Land takes about four days by using carriage (two days on train in the anime).

Layout
Lindwurm is home to a massive church that looks like it’s been carved directly out of the mountain, and the townscape laid out below it has whitewashed buildings. The main street running through the town is swarming with tourists, and it ends in a long set of stairs leading directly to the church.

Lindwurm has also developed into a major city second only to the Midgar Kingdom since the construction of the reservoir dam, which maximized its abundant water resources. The dam's development also consisted of improving the Sacred Land's water and sewage systems and building multiple aqueducts throughout the city.

As a result, there are an increased number of small and large underground facilities at an accelerating rate to the point where no one could keep track on all of them.

Trivia

 * A lindworm (worm meaning snake), also spelled lindwyrm or lindwurm, is a mythical creature was said to live in the forest in northern and central European folklore, traditionally having the form of a gigantic snake monster.  It can be seen as a kind of dragon.
 * In the anime, before starting the Trial, Nelson steps on a hidden switch at his feet to activate the barrier. At the time when Cid summoned Aurora, Nelson said, "I haven't moved it yet," suggesting that the Cult of Diablos can control whether or not to summon the warrior spirit.