Maintenance for the week of April 22:
• [COMPLETE] PC/Mac: NA and EU megaservers for patch maintenance – April 22, 4:00AM EDT (08:00 UTC) - 9:00AM EDT (13:00 UTC)
• Xbox: NA and EU megaservers for patch maintenance – April 24, 6:00AM EDT (10:00 UTC) - 12:00PM EDT (16:00 UTC)
• PlayStation®: NA and EU megaservers for patch maintenance – April 24, 6:00AM EDT (10:00 UTC) - 12:00PM EDT (16:00 UTC)
Imperial City Sewers. At the very center of the map is an "event". It culminates with you fighting Molag Bal. Beat Bal, finish the event, get achievement.
Definitely bring a group with you or do it when there are at least a handful of your alliance members there. Your dealing with mobs + enemy alliance players.