The challenge maps include Osgiliath and Lorien. The former is for characters levels 4-16, while the latter is set for levels 11-22. Both can be accessed as soon as they are unlocked by reaching the second hub area in the game. The challenge maps also include a Fellowship symbol that allows the party to transport directly back to town making them easy to hop in and out of without disrupting progress in the main storyline.
According to the blog, "Challenge maps are a great way to get bonus XP, loot, coins and achievements! Upon completing each of the challenge maps you will get a lump sum XP bonus on top of any bonuses you got along the way!"
The Lord of the Rings: War in the North is due to be released in NA on November 1, and EU in November 25.