Arda is the earth of the Lord of the Rings. It is the land intended by the Iluvatar to be the land of his children, as it was conceived in the Ainulindale. Before it was marred by the evil of Melkor (Morgoth), it was a land of plenty, a symmetrical land of beauty. All of this changed with the destruction and upheaval caused by the war between the Valar and Melkor for domination of the land.
At the point where the Valar had completed as much of the Vision as they could, Arda was round and flat, encircled by the outer sea (Ekkaia), which in turn was enclosed within the walls of the night. It contained two great continents, Aman and Middle Earth (Midgard), separated by Belegaer, the Great Sea. Below the Plains of Arda was a great expansive rock and caves. Whether this rock rested upon anything or not is not said. Above the Plain of Arda was the atmosphere.
When the change came, Iluvatar removed Aman from Arda and made Arda the round sphere that it is today.
We will be at first dealing mostly with the late Third Age of Arda, the time of the Hobbit and the Lord of the Rings, but we will also cover material from earlier times, including all of the Third Age and the times of legend. So welcome to our endeavors and we hope you enjoy the material presented here!