This is a mostly structured route around Lake Washington that is popular with road biking. With the exception of miles 21.5-28.5, through the streets of Bellevue, it follows the lake with spectacular views including views of Mount Rainier across the lake. The majority of the path is on protected trails including a stretch at the beginning through the Washington Arboretum for 2 miles and the last 10 miles on the Burke-Gillman trail. The path runs adjacent to many parks and restrooms so self supporting is quite easy. From miles 19.52-20.37 there was trail rehab so the adjacent pathway was used and it would not affect the distance. At mile 32 the traditional bike loop follows straight north along 100th but before it joins the Burke-Gillman trail to the north, it goes down a very steep and windy hill with no sidewalks or shoulders, so a path chosen follows a safer route closer to the water and adjacent to St. Edwards Seminary Park. With the exception of occasional trail repairs this route would not require alternate paths in the future.
The route is interesting for folks to run because it circumnavigates the lake separating Seatte from the eastside suburbs, through some great city parks with views of the lake, beaches and mountains. It is easily accessible and since it is a loop it can be run in either direction. The route starts on the west at UW Husky stadium, past the Renton Airfield to the south, past the Seahawks training facility (VMAC) on the east and past the Kenmore Air Harbor to the North.
Donut: A 100k variation of this route adds another 14.7 miles and 700' of elevation gain and loss with a loop around Mercer Island. In this version, the route starts and ends at Enatai beach park, and runs a loop around Mercer Island as well as the standard Lake Washington Loop, plus the connecting bridge. While the Lake Washington Loop section is on protected trails or sidewalks for the most part, the Mercer Island loop is on unprotected shoulder for about 10 miles, so caution must be taken while running as there are some blind corners.
Going for the FKT on this variation tomorrow (2/20/21), supported style.
To clarify, going for the FKT on the Donut variation (the 100k version).