Mill Lake Park is the easy outdoor stop in central Abbotsford, with a flat loop trail, boardwalk sections, picnic areas, and water views in the middle of the city. It is not wilderness, but it is useful if you want fresh air without driving out to Sumas Mountain.
The lake also gives a small window into Abbotsford's logging past: the area was once tied to sawmilling before it became the city's best-known urban park. Come for a short walk, not a full day.