Tirion upon Tuna is the fictional metropolis which appears in J.R.R. Tolkien's fantasy novel "The Silmarillion"
Located between the dark shadowy waters of the great ocean and the bright lands of the blessed realm of Aman, where the Powers dwell.
Tirion was built by the Vanyar elves in the Calacirya, a valley which connects the two realms, the only place in Aman where light filters through the margin of the encirceling mountains,, The Pelori, and illuminates the other side.
On a hill named Tuna, lies the shadowy city of Tirion.