how do I leave the city in dragon age 2?

Answer 1

if you exit a zone  you will see a map and you will have the option of going to kirkwall in daytime, kikrwall in nighttime, or outside kirkwall (look for icons on bottom right corner)

Answer 2

You first have to be tasked missions that lead outside of Kirkwall before being able to leave the city.

Answer 3

you have to get a quest that allows you to leave the city