Question: Which fictional location is featured in the children's novel published fourth in "The Chronicles of Narnia" series by C. S. Lewis?

Context paragraphs:
Underland (Narnia): The Underland is a fictional location in the children's fantasy series "The Chronicles of Narnia" by C. S. Lewis.  Described by Lewis as lying beneath the land of Narnia, Underland appears mainly in The Silver Chair, where Eustace Scrubb and Jill Pole travel under the ground to reach it in their search for Prince Rilian.  They find him in Underland and release him from his enchantment by The Lady of the Green Kirtle.

The Silver Chair: The Silver Chair is a high fantasy novel for children by C. S. Lewis, published by Geoffrey Bles in 1953.  It was the fourth published of seven novels in "The Chronicles of Narnia" (1950–1956); it is volume six in recent editions, which are sequenced according to Narnian history.  Like the others, it was illustrated by Pauline Baynes and her work has been retained in many later editions.

The Voyage of the Dawn Treader: The Voyage of the Dawn Treader is a high fantasy novel for children by C. S. Lewis, published by Geoffrey Bles in 1952.  It was the third published of seven novels in "The Chronicles of Narnia" (1950–1956) and Lewis had finished writing it in 1950, before the first book was out.  It is volume five in recent editions, which are sequenced according to Narnia history.  Like the others it was illustrated by Pauline Baynes and her work has been retained in many later editions.  It is the only Narnia book that does not have a main villain.

Narnia (world): Narnia is a fantasy world created by C. S. Lewis as the primary location for his series of seven fantasy novels for children, "The Chronicles of Narnia".  The world is so called after the country of Narnia, in which much of the action of the Chronicles takes place.

The Chronicles of Narnia: Prince Caspian: The Chronicles of Narnia: Prince Caspian is a 2008 high fantasy film based on "Prince Caspian", the second published, fourth chronological novel in C. S. Lewis's epic fantasy series, "The Chronicles of Narnia".  It is the second in "The Chronicles of Narnia" film series from Walden Media, following "" (2005).  The four Pevensie children (William Moseley, Anna Popplewell, Skandar Keynes, and Georgie Henley) return to Narnia to aid Prince Caspian (Ben Barnes) in his struggle with the "secret" help of Aslan (Liam Neeson) for the throne against his corrupt uncle, King Miraz (Sergio Castellitto).  The film was released on May 16, 2008 in the United States and on June 26, 2008 in the United Kingdom.

Aslan's Country: Aslan's Country is a fictional location from C. S. Lewis' "The Chronicles of Narnia" series.  It is the home of Aslan, the great lion.  It is described as a series of mountains, thousands of feet high, but without snow or ice.  Instead, Aslan's Country has a clear blue sky, lush green grass, colourful birds, and beautiful trees.  There are entrances to Aslan's Country from all worlds, including Narnia and Earth.  It is located beyond Narnia's rising sun at the eastern edge of the world, and indeed rings around the whole Narnian world.

Mr. Tumnus: Tumnus is a fictional character in C. S. Lewis' series "The Chronicles of Narnia".  He is featured prominently in "The Lion, the Witch and the Wardrobe" and also appears in "The Horse and His Boy" and "The Last Battle".  He is close friends with Lucy Pevensie and is the first creature she meets in Narnia, as well as the first Narnian to be introduced in the series.  Lewis said that the first Narnia story, "The Lion, the Witch and the Wardrobe", all came to him from a single picture he had in his head of a faun carrying an umbrella and parcels through a snowy wood.  In that way, Tumnus was the initial inspiration for the entire Narnia series.

Prince Caspian: Prince Caspian (originally published as Prince Caspian: The Return to Narnia) is a high fantasy novel for children by C. S. Lewis, published by Geoffrey Bles in 1951.  It was the second published of seven novels in "The Chronicles of Narnia" (1950–1956), and Lewis had finished writing it in 1949, before the first book was out.  It is volume four in recent editions of the series, sequenced according to Narnia history.  Like the others, it was illustrated by Pauline Baynes and her work has been retained in many later editions.

The Chronicles of Narnia: The Silver Chair: The Chronicles of Narnia: The Silver Chair is an upcoming fantasy adventure film based on "The Silver Chair", the fourth novel published in C. S. Lewis's epic fantasy series "The Chronicles of Narnia" (and sixth in internal chronological order).  It is intended to be the fourth installment in "The Chronicles of Narnia" film series, and the first film in the series to be produced by C. S. Lewis Company.  This will be the first film in the series to be distributed by TriStar Pictures and Entertainment One and the first not to have the involvement of Walden Media.  The film's release date has yet to be announced.

Lucy Pevensie: Lucy Pevensie is a fictional character in C. S. Lewis's "The Chronicles of Narnia" series.  She is the youngest of the four Pevensie children, and the first to find the Wardrobe entrance to Narnia in "The Lion, the Witch and the Wardrobe".  Of all the Pevensie children, Lucy is the closest to Aslan.  Also, of all the humans who have visited Narnia, Lucy is perhaps the one that believes in Narnia the most.  She is ultimately crowned Queen Lucy the Valiant, co-ruler of Narnia along with her two brothers and her sister.  Lucy is the central character of the four siblings in the novels.  Lucy is a principal character in three of the seven books ("The Lion, the Witch and the Wardrobe", "Prince Caspian", and "The Voyage of the Dawn Treader"), and a minor character in two others ("The Horse and His Boy" and "The Last Battle").

Supporting paragraphs: Underland (Narnia) The Silver Chair
Answer: Underland