"The Encantadas or Enchanted Isles" are a series of "sketches," or short prose works, about the Galapagos Islands. They are primarily written from Melville's own experience sailing around the islands; however, it should not be supposed that the narrator is supposed to be Melville himself. In fact, Melville originally published "The Encantadas" under a pseudonym.

Before each sketch is a few lines of poetry, most of them from Edmund Spenser's poem The Faerie Queen.

The first sketch gives the reader an introduction to the "enchanted islands" of the Galapagos. The narrator notes that they are primarily the creation of volcanic ash, built up over thousands of years in the ocean. This volcanic origin is why all the islands are covered with "clinkers"—small, black volcanic rocks. They are very isolated, due to their position far out in the ocean. There are a few dozen different islands. They run along the equator, and so they have a tropical climate, and no seasons. With a few exceptions, the islands are uninhabitable, owing to a lack of water, food and shelter. The only animals are primarily reptilian: snakes, lizards and tortoises, with a few million giant spiders thrown in for good measure. Most plants are tangled and prickly. The area is difficult for sailors to visit, due to the strange sea currents created by the island chain. The narrator ends the description by noting that he is sometimes affected by an optical illusion, in which he seems to see a tortoise crawling toward him with the word "Memento…" in flaming letters on its back.

The second sketch describes an encounter between the narrator and a tortoise. The ship's crew brings three tortoises aboard, and the narrator examines them closely. He is fascinated by how ancient they seem to be, judging from the old cracks and scars on their shells. He also notes their stubbornness, as they attempt to push over or through any object they encounter when walking: "Their crowning curse is their dredging impulse to straightforwardness in a belittered world." The next night, however, the tortoises are served for dinner, and their shells are hollowed out and made into giant soup-bowls.

In the third sketch, the narrator tells us about the Rock Redondo, a huge stone tower situated on one of the islands. Over two hundred feet tall, the Rock affords a grand view of its particular island and the surrounding ones. The narrator observes that many sea birds make their nest along the naturally- occurring tower, beginning with penguins at the bottom, proceeding through various gulls and pelicans until reaching the large sea gulls at the top. The noise of the birds is deafening throughout the day.

The narrator climbs the Rock Redondo in the fourth sketch. After noting how impossibly difficult the climb is, the narrator briefly describes some of the surrounding islands. He then tells the story of how the islands were discovered. For many years, sailors made the journey from Peru to Chile by following near the coast. This was a dangerous route, due to the sea currents. Then a famous pilot, Juan Fernandez, tried sailing further away from the coast to make the journey, and met with great success. In the process of sailing so far out, he discovered the Galapagos Islands. One of the islands is named after him. The narrator describes two islands in particular, Narborough and Albemarle, noting wryly that their population consists almost exclusively of spiders, snakes and lizards.