You find a device that takes you to the future of this huge ruined city that has a overcast rainy feel to it some parts are flooded

Exploring streets buildings sewers etc.

You encounter "the survivors" who are housed in this huge luxury hotel to take on quest from them

The plot there is a mansions outside of the city where "the witch" lives
you'll have to go through a creepy forest to reach her

"the survivors" think she has the powers to grant wishes i.e. to restore the city to it's original state

two words. riding. dragons.