Arcata Community Forest provides wonderful hiking opportunities on ten miles of trails as well as picnicking only a few minutes from downtown. Second-growth redwoods tower overhead on the many trails.
If you go:
Parking, drinking water and restroom facilities, as well as picnicking, at Redwood Park. No water or restrooms on trails. Pack out trash. Horseback riding and mountain bikes limited to roads.
Links:

Redwood Park
Parking lot at east end of 14th
Alternate parking off Fickle Hill Rd
Arcata, California 95521 USA
Mailing address:
Arcata Recreation Division
736 F Street
Arcata, CA 95521 USA
Phone Numbers:
Arcata Recreation Division
+1 (707) 822 ext. 8184
+1 (707) 822 ext. 8184