The Prado is a difficult museum for a visitor to manage, for it is filled with spectacular mountains of great art. No other museum in the world can rival its enormous collections of Spanish artists such as El Greco, Velazquez and Goya and even of foreign artists such as Hieronymus Bosch. It is easy to get lost in one of the mountains, spending a magnificent afternoon with Velazquez, for example, and having no time left for anyone else.

If you have no more than an afternoon to spend at the Prado museum, you can feel a little regretful for missing so much. But curator Javier Portus has come up with an extraordinary special exhibition that leaves you with a wonderful sense of completeness. This exhibition, “The Spanish Portrait: From El Greco to Picasso,” draws on the great riches of the Prado, adds stunning loans from elsewhere and combines them to tell a coherent and satisfying story.

The exhibition, which displays 87 paintings, almost half from the Prado, closes Feb. 6 and goes nowhere else. By its very nature, it cannot, for the Prado would have to part with some of the greatest splendors of its Spanish collection for the show to make sense elsewhere.

The show is enhanced by the fact that most of Spain’s finest artists painted many portraits. Portraiture, after all, was the main livelihood of Velazquez and Goya, hired as court painters to turn out portraits of the royal family. The show makes clear that the great Spanish painters for more than four centuries studied the portraits made by their predecessors and kept those paintings in mind as they produced their own work. Yet despite the obvious importance of portraiture to these great artists, the exhibition, as Portus points out in the catalog, “is the first large-scale attempt to trace the development of the portrait in Spain.”

The most striking of the early portraits is probably El Greco’s “A Nobleman With His Hand on His Chest,” painted between 1577 and 1580. El Greco, born on the Greek island of Crete and given the name Domenikos Theotokopoulos, produced most of his paintings while living in Spain. Although best known now for his expressionist distortions in landscapes and religious paintings, his portraits were remarkably realistic. With the intensity of the model’s gaze and the sincerity of the gesture of his hand, this painting, in fact, looks like a prototype for a Velazquez.

Diego Velazquez, born in Seville, was appointed a court painter as a young man in Madrid in 1624, a decade after the death of El Greco. He clearly admired the old master and later kept three El Greco portraits in his apartment. It did not take long for Velazquez to surpass the painter he admired. As Alfonso Perez Sanchez, an art historian and former director of the Prado, puts it in the exhibition catalog, “Velazquez very soon proved to be an exceptional interpreter of the human soul.”

Spanish artists and historians have long kept Velazquez in an exalted position in Spanish art. His place is much like that of Shakespeare in English literature. Even the greatest Spanish artists pay tribute to Velazquez and set his work as a standard to which they must strive. It is no accident that one-fifth of the portraits in the exhibition are by Velazquez. The fervent adulation for him was made clear by the anguish in Madrid in 1898, when rumors spread that American art collectors wanted the U.S. government to take all the Velazquez paintings in the Prado rather than the Philippine Islands as booty in the Spanish-American War. In the end, Spain lost the Philippines but not the paintings.

As the exhibition makes clear, Velazquez had a genius for painting dwarfs as meaningfully as kings, or buffoons as seriously as noblemen. In “Pablo de Valladolid,” painted around 1635, Velazquez dresses the court actor (or perhaps the court jester) in the black suit of a nobleman, but the movement of his hands and legs betrays Valladolid as a performer.

The Prado’s signature canvas

The stellar attraction of the exhibition is Velazquez’s 1656 group portrait “Las Meninas” (The Maids of Honor). Perez Sanchez, the art historian, calls it “the culmination of Velazquez’s art.” There are several foci, several stories going on at once.

The Infanta (or Princess) Margarita, a graceful child with the hint of mischievous eyes, is looking right at you as you stand in front of the painting. But as you shift your gaze to Velazquez on the left side of the portrait, it is obvious that he is painting someone standing just where you are. A mirror at the back of the room reveals that the model is a couple -- the king and queen of Spain. So Margarita is looking at her parents, not you. The painting also depicts two maids of honor waiting on Margarita, a pair of dwarfs disturbing the sleep of a dog, a pair of chaperons chatting in the background and the queen’s chamberlain standing in the doorway and surveying this portrait of everyday life in the palace.

The Prado never loans the painting. Perez Sanchez told me more than 10 years ago, when he was director of the museum, “You cannot come to the Prado and fail to find ‘Las Meninas.’ It would be like coming to Paris and not seeing the Eiffel Tower.”

A great tribute to Velazquez came more than a century after his death when Francisco de Goya, born near Zaragoza in the province of Aragon, won appointment as a court painter in Madrid. Goya was steeped in the works of Velazquez. He had even created a series of engravings of Velazquez paintings, including “Las Meninas.” One of the great treats of the exhibition is to find Goya’s group portrait “The Family of the Infante Don Luis” in the same room as “Las Meninas.” “The Family of the Infante Don Luis,” painted in 1783, was obviously heavily influenced by Velazquez. But it does not imitate “Las Meninas” as much as pay homage to it.

The Goya painting is not well known, for it was in private hands for almost 200 years and only became the property of the Magnani-Rocca Foundation in Parma, Italy, in 1974. Don Luis was a kind of disgraced prince kept in exile far from Madrid. Goya painted him as a vacant, elderly man playing with cards while his much-younger wife, attended by her hairdresser, looks vital and in control of the household. The retinue, depicted with so much care that each individual exudes a different personality, includes family and servants, among them a secretary who may be the wife’s lover. In a direct allusion to “Las Meninas,” Goya included a portrait of himself painting the scene from the left corner of the canvas.

In another unique pairing, the exhibition has placed Goya’s two portraits of the Duchess of Alba near each other. The first, painted in 1795, is owned by the Alba family; the second, painted in 1797, is owned by the Hispanic Society of America, which never before let it travel from the society’s museum in New York. “The Duchess of Alba,” a French traveler once wrote, “possesses not a single hair that does not awaken desire,” but many find her more haughty than seductive in Goya’s portraits.

In the second portrait, she sports a pair of rings, one inscribed “Goya,” the other “Alba,” and points to the ground where the words “Solo Goya” (Only Goya) have been drawn in the sand. This has fueled 200 years of speculation about an affair. Novels and movies about Goya usually feature torrid scenes between the two. But French writer Jeannine Baticle, the authoritative biographer of Goya, and art historian Janis Tomlinson, the American specialist on Goya, do not believe that any romance ever took place.

Portrait painting was popular in Spain during the 19th century, and the exhibition features a variety of works from that era. The most notable are probably Federico de Madrazo’s “The Condesa de Vilches,” painted in 1853, and Ramon Casas’ “Santiago Rusinol,” painted in 1889. Madrazo knew Spanish portraiture well, for his father was director of the Prado, but the painting owes a great deal to the influence of his friend, the renowned French portrait painter Jean-Auguste-Dominique Ingres. Casas, on the other hand, studied in France but with a teacher who idolized Velazquez. Casas’ portrait of Rusinol is in the Velazquez tradition and, in tribute to the 17th century master, the portrait shows a piece of a reproduction of “Las Meninas” on the wall in the background.

Casas and Rusinol led a group of Art Nouveau artists who met at Els Quatre Gats Cafe in Barcelona at the turn of the 20th century. Pablo Picasso joined them as a teenager and even exhibited at the cafe before moving on to Paris. The Prado exhibition closes with several portraits by Picasso, the most unusual a haggard, depressed self-portrait painted in 1901 when the artist was hungry, lonely in Paris and shocked by the suicide of a friend.

Picasso is usually regarded as a revolutionary painter who broke new ground in the 20th century, but he never forgot the tradition that nurtured him. In 1957, for example, he painted 44 canvases that are all variations on the theme of “Las Meninas.” Spanish art historians detect the influence of El Greco on his early portraits. Prado Director Miguel Zugaza Miranda writes in the catalog that “an unbroken line [in Spanish portrait painting] can be traced from the 16th century to Picasso.” There is ample evidence for his conclusion.