The Guarded Realm of Valinor (somewhat conjectural)

A name given to the domain of the Valar in the Blessed Realm of Aman, surrounded by mountains that guarded it from Melkor and his allies. It may have been guarded by other forces besides, but at the most crucial of times the Guarded Realm was found unprotected by Melkor. Having recently escaped from the Valar, he had recruited the great spider Ungoliant and used her webs to scale the southern mountain-fence at a time of festival. The land of Valinor lay open before him, and he swept down with Ungoliant to attack the Two Trees and bring about the Darkening of Valinor before he escaped the Guarded Realm and fled to Middle-earth.