where was how green is my valley filmed

The film "How Green Was My Valley" was primarily filmed in California, not in Wales where the story is set. Plans to shoot in the Welsh Rhondda Valley were abandoned due to World War II. Instead, an 80-acre set of a Welsh mining village was constructed at Brent's Crags in the Santa Monica Mountains near Malibu, California. This set was built to resemble actual Welsh villages like Cerrig Ceinnen and Clyddach-cum-Tawe. The movie was shot mostly at the 20th Century Fox Ranch in what is now Malibu Creek State Park in California. The village set and coal mine scenes were all filmed there, creating an authentic representation of the fictional Welsh town portrayed in the film.