Lo lógico es usar el verbo 'ser' y no 'estar'. 'El valle es bello' si sería correcto.
Vladdy, Since the use of the verb is for description, you go with SER. I couldn't remember if el valle was masculine or feminine, but now I think of Rudy Vallee, the old American (from the United States of America) singer, and remember it's masculino.
In the translation I weote Vaale instead of Valle. It is a typing mistake, of course.