Fafner in the Azure is a very underrated anime that definately needs more attention. Basically, the world has been decimated by large golden aliens called Festum. Cities to countries, including most of Japan are no more and only a small portion of percentage of the population had survived. However, a small Japanese island is left untouched and live their lives as if nothing has happend. During this time, technology has definately advanced and life goes on peacefully until the Festum return.
Teenagers are the pilots of mecha called Fafners, robots capable of fighting back the Festum, and soon the UN has recruited the fighters of the small island to fight back against the aliens for the entirety of humanity.
It's a very good anime with excellent animation, wonderful art style (which is shocking similar to that of Gundam Seed) beautifully soundtrack, great characters, and a great plot and storyline.
I would highly recommend it for those who like Mecha, Drama, and some Tragedy. For those who like Evangelion, Gundam Seed (or any Gundam series for that matter), Macross (in a sense), Eureka Seven, or Stellvia of the Universe (an also undercredited anime).
It has its share of hope, tragedies, philosophical nature and more.