Pendrell Vale
Pendrell Vale was located on Tolaria. It is known for its The Tabernacle at Pendrell Vale, Pendrell Mists, and Pendrell Drake. The vale emanated strange magics that inhibited the use of summoning magic, allowing any mages tapping into its power to force their foes to expend great quantities of mana to keep summoned creatures from disappearing into nothingness. These strange properties may have been a result of Urza's failed time travel experiments.
After the destruction of Tolaria, Pendrell Vale's magic continued to emanate, calling out to certain wizards who took to worshiping the ancient Tabernacle. As such it is probable that Pendrell Vale alone survived the island's ruin.