Mage tower

Serpentine spires of living rock form the foundation of the mage towers where glowing spheres of mystic energy serve to replenish and focus the awesome magiks wielded against the Orcish Horde. These towers hold ominous secrets that none but the mages of Lordaeron dare to explore. As extensions of the Violet Citadel in Dalaran, these towers allow the mages to research arcane spells, unfettered by the affairs of the temporal plane.

In the Third War, their function was replaced by the arcane sanctums.

Also, they look a lot like the Guard Towers of the Third War, except without the ballista arrows and with a taller point.

In World of Warcraft
Many mage towers (of a different design than the ones used in the Second War) exist in WoW, the largest being Wizard's Sanctum in Stormwind City.

Other mage towers:
 * Tower of Azora
 * Tower of Ilgalar
 * Tower of Althalaxx
 * Theramore's castle
 * Tower of Arathor (may just be the same model)
 * Durnholde Keep's Tower (Caverns of Time only)
 * Northwatch Hold's Tower
 * Klaven's Tower
 * Nethergarde Keep's Tower
 * Azshara Tower
 * Hearthglen's Tower
 * The tower at Amber Ledge.