The new game mode sounds a lot like World of Warcraft's Arathi Basin.Summoners!
Many of you may have been wondering out loud just what we have in store for the future. Today we are pleased to give you your first look at League of Legends: Dominion, the largest game update in the history of League of Legends. This update will feature not only a brand new map, but also an entirely new game mode showcasing innovative gameplay never before attempted in the MOBA genre.
For quite some time, all of you have been clamoring for new battlefields upon which to test your skills against other summoners in League of Legends. We're pleased to announce that we've heard you, and that for over a year our Design Team has been working tirelessly to craft Dominion into a truly new and groundbreaking experience.
http://na.leagueoflegends.com/news/leag ... ion-coming