The Silver Enclave is the Alliance district of Dalaran and the headquarters of the Silver Covenant, a group of high elves opposing the inclusion of the blood elves into the Kirin Tor. When any Horde members approach the Enclave, they are immediately teleported away by the guards.
The area is home to a Hero's Call Board, Class Trainers for all classes, a mailbox as well as Quartermasters for many Legacy currencies upstairs.
All areas are patrolled by Silver Covenant Guardian Mages.
When first opened, the area contained portals to all Alliance Cities, as well as a portal to Wintergrasp whilst under Alliance control, and Portals for all PvP battlegrounds (although this is shown and labelled as portals, it served as an access to the battleground dialogue boxes).
Horde members can get by guards by having a paladin bubble them. This will cause the guards not to be able to target you and you can stay inside the building as long as you don't enter a new area of the building while un-bubbled. However it is not recommended to do so as you may be punished by the Game Masters.
It is also possible for a death knight to use their Army to overload the teleport, though it is difficult to maneuver the Army even with a permanent Ghoul. This can only be done to enter the Hero's Rest, as the hallway leading to the capital city portals is within Line-of-Sight for the Guardian Mages.