The Toronto DIY Ultramarathon is an 83(ish) kilometer loop that takes advantage of the interconnected trails that run around and through the largest city in Canada.  The loop consists of 28km of road and 55km of trails, both paved and dirt.  There are 24 hour Gas stations at 10-25 kilometer intervals along the trail, so it is very conducive to self-supported attempts.   Water fountains and public restrooms are also located along the route which are seasonally operational.