In the early versions of Tolkien's mythology (see The History of Middle-earth) the city was called Kôr.
The green hill of Túna was located in the steep-walled valley of Calacirya ("The Cleft of Light" in Quenya), the only pass through the mountains of the Pelóri. Upon the crown of the hill the Elves raised their largest settlement west of the sea, Tirion. The walls and terraces were white, and the sand in the streets was said to be of grains of diamond, and white crystal stairs climbed from the fertile land beneath to the great gates.
The center of the city was dominated by the High King of all Elves Ingwë's tower Mindon Eldaliéva, whose silver lantern shone far out to sea. Beneath the tower was the house of Finwë, first High King of the Noldor. Here also was the Great Square, where the white tree Galathilion flourished, and later the site of Fëanor's infamous oath.
After most of the Vanyar elves resettled to the base of Mount Taniquetil, the rule of Tirion was given to Finwë. Many years of bliss followed, until Tirion was shaken by the King's eldest son, Fëanor. After the murder of his father at the hands of the dark Lord Morgoth and the theft of his most precious gems, the Silmarils, Fëanor assembled the Noldor at the Great Square. There he urged them to go back to Middle-earth to avenge their king and reclaim the Silmarils, and to see that their lives in Tirion were simply a prison brought upon them by the Valar. In the end only a tenth of the population remained in Tirion when Fëanor and his people departed, though some followed their new king only reluctantly, and some would soon abandon Fëanor and follow Finarfin back to Tirion.
Nearly 600 years passed before Tirion once again appeared in the mythology. When all the elven kingdoms in Middle-earth were in ruins, the half-elf Eärendil sailed into the West in search of Valinor to ask for the assistance of the Valar in the war against Morgoth. Eärendil arrived in Tirion on a day of festival when the city was all but empty, and only when he had turned his back on the city and began to return was he approached by a herald of the Valar. His coming led to the War of Wrath and the end of the First Age.
More than 3,000 years followed before Tirion was for the first time seen by mortal eyes. Soldiers of the king of Númenor, deceived by Sauron, landed in on the shores of Eldamar and camped around Túna, which the fleeing elves emptied. When the men of Númenor were buried under falling hills, Tirion, along with all the Undying Lands, was taken out of mortal reach forever.