Sehome Hill Arboretum is a 65-hectare forest park managed jointly by the city and Western Washington University, whose campus edges up to the lower slopes. A network of hiking trails climbs through second-growth Douglas fir and madrone to a stone observation tower at the summit, where on a clear day you can see Bellingham Bay, the San Juan Islands, the Olympic Mountains, and the snow cone of Mount Baker all at once.
The arboretum is genuinely well maintained, with good trail signage and a diversity of native and introduced species that make it worth a slow walk at any time of year. The trails are used constantly by WWU students, faculty, and local runners — a good sign that this is a real park rather than a tourist attraction. The main trailhead is just off Bill McDonald Parkway near the university entrance.