Like many of E. Nesbit's books, the story is a fairly episodic series of more or less separate adventures, but some elements of the story are carried across different parts of the book. One of these is my favourite bit of magic from the story, the most 'enchanting' aspect and the one that makes the 'enchanted castle' really, properly enchanted since it seems to have little to do with the magic ring that otherwise dominates the plot (except that you must be wearing the ring in order to see them move) - the statues in the castle grounds that come to life at night. The gardens are described as like dreams during the day and like visions at night, and the image of groups of white, cold statues (they 'come alive' but stay made of marble) moving about the moonlit garden in summer is pure magic.
The statues are chiefly on two subjects - dinosaurs, which are specifically compared to those at Crystal Palace Park that I've mentioned before, and classical subjects. Just as in C. S. Lewis' later Narnia stories, the first of these magical creatures encountered by one of the children is a creature with goat's legs and the head and arms of a boy - a faun. This description could apply to either a faun or a satyr, but the woodland setting and the location, near the Temple of Flora (a Roman goddess) suggests a faun. Just like in Narnia, the faun is a woodland spirit who embodies the magic of the woods, making him a perfect introductory character for a magic wood (although the setting is an enchanted garden, it is the sort of very large, estate 'garden' that more resembles a wood in places).
Gerald discovers the faun and the dinosaur quite early on in the book, but the enchanted garden really comes into its own much later, when Kathleen accidentally gets turned into a statue herself, and 'comes alive' together with the other statues in the garden. Kathleen and Mabel make friends with a statue of Phoebus Apollo, who declares himself to be their slave and whisks them off - Mabel having become marble as well - for a night in 'his world', a magic world of living marble with seven moons reflected in the lake. There, they enjoy a 'celestial picnic' with an array of classical deities, including Zeus, Dionysus, Hera, Hermes, Hebe, Psyche, Eros and Aphrodite Urania.
During the feast, having fetched the boys, the gods hint that the origin and secret of the magic ring, which is at the heart of all the magic, is something to do with them, but dawn comes before they get around to explaining anything. Hermes tells the children when they can come back and, for one night only, talk to the statues and ask them questions without the ring. Various plot developments involving the childrens' French governess result in the French governess, her fiancee and the children reassembling on the night in question, and seeing not only the Olympian gods but all the ancient gods of Egypt and Assyria as well. The magic ring was apparently given to a mortal once, and the story ends romantically as the French governess wishes all magic away from it, leaving it to be simply her wedding ring. Magic rings are notable for their absence from Classical mythology, and I can't think of any from Egyptian or Assyrian mythology offhand either - with the exception of Plato's parable of the Ring of Gyges, magic rings are much more the province of Norse mythology (Tolkien's inspiration). I'm not sure if Nesbit is referring to a story she expects her readers to know, or if this is an invention of her own.
Like Fantasia, this story brings some magic into classical mythology, something which is sometimes lacking in other uses and re-tellings. The gods become approachable, friendly - all are described as amiable, lovely, just like your mother and so on. There is nothing terrible or frightening about them, though there is a sense that they are awe-some, in the most literal sense, when our heroes go to see them on the appointed day. In addition to the major Olympian gods, the focus is on those who are associated with parties, love and joyful things - Hebe the cupbearer, Eros, Psyche, the mortal wife of Eros. This is, perhaps, not the most faithful representation of classical mythology ever written, since it omits any sense of strife, discord or violence. On the other hand, nectar and feasts of the gods and celestial parties are, indeed, part of classical mythology, so perhaps it is better to say that Nesbit has carefully selected those aspects of classical mythology that best suit her purpose. And the result is that, like Fantasia and like Nesbit's depiction of ancient Babylon in The Phoenix and the Carpet, this story makes classical mythology something far more appealing, far more magical and wonderful, to young readers than drier, sometimes more faithful, re-tellings. The less pleasant aspects of Greek mythology are generally not very suitable for children anyway, so it can be fun to indulge in something a joyously warm, comforting and 'enchanting' as this story.