The walk starts near MOHAI (Museum of History and Industry). If you want to see this, get there soon, because the new 520 bridge will require its removal. It will probably resurface somewhere else, but its current venue is a pretty nice location, with several Seattle memorabilia (like a Ben Bridge Street Clock and a gun from an old battleship).
We followed the walk out to Marsh and Foster Islands, skirting along the edge of Lake Washington where it flows into the Montlake Cut:
The millfoil is severe. It's pretty bad in the calmer sections of water, but at least the flowers are pretty.
This is another instance of a locale that we really should have visited before this; we've been in Seattle how many years and this is our first (well, second, but a couple of months ago didn't really count) time enjoying these islands? It was a really nice stroll on the trail through the dense foliage. We crossed the second bridge from Marsh to Foster Island and made our way out to the point on the north side. Lots of people were enjoying kayaking, sailing, rowing, picnicing.
We continued on the walk passing under 520 and then going through some more marshland, finally making our way to the Arboretum's Visitor Center. (They were setting up for a wedding, but happily it hadn't started so we were able to enjoy several gulps of cold water.) We briefly visited the botanical garden before turning back West to enter the Arboretum proper, crossing over Lake Washington Boulevard: We continued on, exited the Park, then walked several more blocks through the quiet Montlake neighborhood (except where it is near 520 or 23rd Avenue). A great walk on a hot day.