The Lake Lansing Trail begins and ends at Lake Lansing Park North in Haslett, MI. It is mildly technical with rolling hills and one larger climb. This FKT follows the Blue Trail, which is the most common route, and begins and ends at the parking lot by the trailhead. The "Lake Lansing from Sandhill" segment on Strava tracks the leaderboard for this trail and has been very competitive amongst mid-Michigan runners for years.

https://www.strava.com/segments/9495039

Running 10 laps is a little over 50km.

This trail runs between Pineland, Texas to near Hemphill, Texas. It was created in 1981 and funded by the Sierra club. Officially the trail is 26.8 miles. There is no water refill sources. 

ENGLISH:

This is the Main Świętokrzyski Trail (GSS) from Kuźniaki to Gołoszyce. 
https://podrozebezosci.pl/glowny-szlak-swietokrzyski-gss-porady-praktyc…

POLISH:

Początek trasy Kuźniaki koniec Gołoszyce 100km. Biegowo cały czas czerwony szlakiem dystans 92 km 2755m w górę oraz 2664 mw dół. Czas brutto 9:59:42 link 

Hartman Rocks Recreation Area has a large network of trails just outside of Gunnison, CO.  During March 15 - May 15 each year about half of the park is closed for protected sage grouse.

Upper Loop (~19 miles):  Josh Eberly recommends the following loop as the "best half of Hartmans you could do without crossing in protected Sage Grouse area":