Avatar: Legend of Korra takes place 70 years after Avatar: The Last Airbender. Korra is the next Avatar after Aang, "a passionate, rebellious, and fearless teenaged girl" who is hotheaded, independent and "ready to take on the world". Korra comes from the Southern Water Tribe, and Aang and Katara's son Tenzin is her Airbending teacher. 
One of the story's settings is Republic City, a "metropolis powered by steampunk-type technology," "inhabited by people from all nations." Here Korra must deal with rampant crime and an anti-bender revolt.
Sweet new Avatar Series!