The tour walks you through the two cloisters, where most of the interest sits, taking in the old refectory, the Gothic hall with its facsimile books, and a small printing museum. You also see the Royal Hall and the monastery church, which carries Renaissance and Neoclassical touches over its older Gothic bones.
King James I founded the place in 1240, a few years after Christian forces took the area from the Moors, and he's a steady presence throughout, down to a reproduction of one of his swords. It sits a short drive north of Valencia, so it makes an easy half-day if you've a car. Guides run in English, German, Italian and Spanish. Closed Mondays, and tickets are only a few euros.