Calacirya

Calacirya (Q, pron. [kaˈlakirʲa]), also known as the Cleft of Light, was the pass in the Pelóri Mountains north of Mount Taniquetil where the Noldorin city of Tirion rested atop Túna. After the hiding of Valinor this was the lone gap through the mountains of Aman. The Valar would have closed the mountains entirely but, realizing that the Elves, even the Vanyar, needed to be able to breathe the outside air, they kept Calacirya open. They also did not want to wholly separate the Vanyar and Noldor from the Teleri on the coast.

Calacirya means "Cleft of Light" in Quenya (from cálë = "light" and cilya = "cleft, gorge").