The Midtown Greenway is a paved multi-use trail in downtown Minneapolis that connects the Mississippi River Trails in the east to the Chain of Lakes paths in the west. It’s ~6 miles one-way through the heart of downtown, roughly paralleling Lake Street. The trail is a good way to see the southern part of downtown, while being completely off-road — either above or below the street. Run any section, or use it as a connector to other trails!
Bonus: The Greenway is lit at night and cleared of snow in winter. Note: the Greenway is sometimes referred to as the Cedar Lake Trail on maps.