The Malibu Creek State Park loop is a loop on pretty popular trails in the Santa Monica Mountains. The easiest access is from the Malibu Creek State Park parking at 1925 Las Virgenes Rd, Calabasas, CA 91302. It is 14 miles long with an elevation gain of about 2,654ft.
A very popular, heavily trafficked trail that runs the length of South Mountain Park in Phoenix. About 15 miles one-way. There is a water fountain at the Pima Canyon TH (east end).
There was a 50 mile race utilizing this trail in 1998-2001, with the CR being Ian Torrance, 7h1m31s in 2000. https://ultrasignup.com/register.aspx?did=12138
"The Dismal Swamp Canal Trail is a former section of Virginia State Rt. 17, now a multi-use trail open to bicycling, walking, running/hiking, horseback riding, and boating. The north trail head is located at the intersection of Dominion Blvd. and Old Rt.
The Pequot Trail is another lovely "blue-blazed" trail managed by the Connecticut Forest & Parks Association. The trail connects Ledyard with Preston and offers occasional views of the Thames River Valley as well as a few gradual climbs, old pastures and overgrown woods roads. at an elevation of 330 feet, Rose Hill is the highest point on the trail. It passes through Preston's Lincoln Park, a recreation area with jogging track, multiple ball fields, and other facilities, following a part of the park's dog-waling trail to Rose Hill Rd.
The "Kaiserkrone" is one of the classic Austrian long distance hikes. The trail starts near "Going am Wilden Kaiser" and circumnavigates the impressive mountain range "Wilder Kaiser". With 65km and 5000m ascent/descent it is usually completed in 5 days. There are several huts along the way, where you are able to eat and sleep.
There is a race called "Kaiserkrone Marathon Trail" (56km, 3800m ascent) which follows parts of the course, however it deviates from the route at several points as it starts in Scheffau not in Going and doesn't pass through Gasteig.
This is a prominent "blue-blazed trail" managed by the Connecticut Forest & Parks Association (CFPA). The following description is courtesy of the CFPA "Connecticut Walk Book". It runs 50 miles N-S from the Cobalt section of East Hampton, CT to West Stafford, CT just shy of the Massachusetts border. The trail traverses the Meshomasic and Shenipsit State Forests primarily on woodland paths and also connects to trail systems in Gay City State Park in Hebron, Case Mountain Recreation Area in Manchester, and Valley Falls Park in Vernon.