Its derelict version of Washington D.C. is eerily beautiful, an incredible experience just to walk around, and full of interesting landmarks and interiors to admire during the large number of missions and activities available. You are mostly doing the same few things over and over and the missions themselves are all, at their core, basically an excuse to take you through a series of closed combat areas that open a path to the next one once you kill all the enemies in that section... but the looting and shooting is quite addictive thanks to its tight mechanics and the amazing scenery you get to visit.
P.S. In case someone is wondering, the campaign is perfectly playable solo, I've reached the endgame on my own all the way through and had no problems.
More info: https://en.wikipedia.org/wiki/Tom_Clancy%27s_The_Division_2