U start out the raid in the sewers, where u have to kill the first bosses in order to advance. Then u reach a middle area where u can chose in what order u progress. Then u make your way to the top and after defeating the people in charge u fight the big bad in a RP fight on the roof.
I think this is a really cool raid design overal and I love it way more then EN.
HFC also had similar design but there we took the front entrance.