The Park to Playa Trail in the Los Angeles area was finally completed in October 2020 with the addition of the pedestrian bridge that connects the Kenneth Hahn Park and the Baldwin Hills. 

Half of it is going through single lane trails and a bit of service roads in the 2 parks, and the other half is a section of a bike path next to the Ballona Creek. It is a very easy route, pretty well marked, with some nice views of the city and the ocean. Bathrooms and water points on the way.

The route information submitted is for the out and back.

La ruta  inicia en el Parque Las Llantas (San Nicolás Totoloapan, Ajusco), en la pluma de entrada al parque y de ahí al parque Los Dinamos 4, tocar la pluma y de regreso.  Es un sendero boscoso y durante el recorrido encuentras de todo, subidas y bajadas técnicas, todo naturaleza, preciosas vistas, arroyos, los árboles durante todo el recorrido te dan sombra que hace que no te desgastes tanto durante toda la ruta.

This is a (mostly) well-marked ~8 mile loop that interweaves some of the Northern portion of RI's North South Trail. Follow orange blazes in either direction from the George Washington Campground's Parking area and bathroom facility (drive through the campground until you see a large bathroom building on your left and a pond beyond it down the hill). This parking area will put you directly on the loop as it passes through the lot. You will not need to pay an entry fee if you go during the off-season, but during camping season, you will have to pay to enter the park.

This route summits 7 mountains in Bear Mountain State Park. This loop starts and finishes at the small gravel lot on 9W; use these coordinates for parking 41.28059, -73.96384 The loop is described clockwise (may be complete either direction).

"The Alpine Slide"... if you're from New Jersey, you'll recognize this name! This 2.8 mi loop with a little over 1,000 ft gain is the former race course of "Running with the Devil" event by NJ Trail Series. This is the perfect trail loop to get some good climbing in by doing repeats. It is an active ski slope so you won't be able to access it during the winter. The loop begins at the base of South Peak Terrain Park.