Below is a summary of selected additional activities in Seattle Centre district.
1) Mobile Command Centre - D.U.P. base is located in the northern part of district. It surrounded by quite high walls but the good idea is that you can get there from any side because it is not adjacent to water. After attacking the base try to quickly destroy enemy watchtowers and watch for snipers (destroy balconies where they are standing) and enemies with supernatural powers. Since the base has few levels you can easily avoid enemy attacks and get to smoke places faster.
2) Blast Shards - One of shards is located over water (western part of district). Start on the nearby metal construction and alternately use hovering over water and Smoke Dash. Try to land on wooden stakes.
Two other drones are attached to the lantern and horizontal bar on the building but in both cases you can catch them by climbing up.
3) Hidden Camera - The camera you're looking for is located in the place shown on the above screen.
4) Audio Log - You have to get to the highest level of the parking. Hard disk is located at the back of the billboard shown on the above screen.