There once was a time when people could sit in the bar of the old Hotel Del Prado and enjoy looking at Diego Rivera's mural, "Dream of a Sunday Afternoon in Alameda Park."

The once elegant hotel is now an earthquake-damaged hulk waiting to be demolished, and the mural is in its own museum pavilion across the street.The delicate transfer of the mural has been completed. It escaped damage in the Sept. 19, 1985, earthquake that killed thousands and devastated large parts of the city.

The famous mural is open to the public again, like a window opened on Mexico's rich history. It shows figures from the Mexican political and art worlds and from daily life all on parade in the park.

An explanation at the entrance to the new museum says the decision was made to transfer the mural from the hotel after the extent of the damage there became clear.

"It should be linked to the Alameda, for having been painted on that theme and for the place itself," the plaque from the National Fine Arts Institute says.

The Alameda, the downtown park across the street and down a block from the mural's old home, also was expanded through earthquake reconstruction programs. A "Solidarity Garden" recalling the victims of the 1985 disaster was built on the site of the cleared, adjoining block that once held a department store and the Hotel Regis.

The mural's pavilion is built on the site of the hotel's parking garage, which was badly damaged and demolished after the quake.

The Fine Arts Institute said that no room could be found in any of its buildings close to the Alameda, "because of the colossal dimensions of the work. . . . That's why it was decided to take advantage of the possibility of constructing an appropriate building."

In place of the old hotel's comfortable cocktail lounge, viewers now can sit on three simple benches placed in front of the mural or just stand for a while in the large but sparsely decorated room. Diagrams, with keyed numbers on the outline of each figure, tell who 73 of the people shown in the mural are.

Among the figures is a fat boy with large eyes and a round face, a self-portrait - something Rivera often put in his works.

In the foreground is Spanish conqueror Hernando Cortes. On a park bench an elderly man dreams of President Antonio Lopez de Santa Anna, giving American Gen. William Scott the keys to Texas, New Mexico, Arizona, California, Nevada and other lands that once belonged to Mexico.

Farther back, a former military man, now poor, dreams of the emperors Maximilian and Carlota. A drunken tramp, next to an old woman, dreams with his mouth open of miltiary glories, at the side of Benito Juarez, who holds the reform laws he put into effect as Mexico's great 19th century president.

Near the center is dictator Porfirio Diaz and his wife, Carmen Romero Rubio. Diaz appears full of his fame and power, with a chest full of ribbons on his uniform.

At the right, a street vendor offers typical Mexican food to a middle-class youth and three students, who dream of Gen. Victoriano Huerta. Official history says Huerta had Francisco I. Madero, who started the 1910-21 Mexican revolution, killed.

Rivera completed the 49 1/2 foot by 13 foot painting for the then fashionable Del Prado in 1948.

Along with David Alfaro Siqueiros and Jose Clemente Orozco, Rivera was one of Mexico's three great muralists and one of the most important Latin American painters in the art world. He died in 1957.

Among his other best known murals are those in the National Palace of the Spanish conquest, the Mexican revolution and other events from the country's history.

"The composition is memories of my life, of my childhood and my youth, from 1895 to 1910," Rivera wrote after finishing the mural. "I do not believe that this work has alarmed or can alarm anyone. The contemporary figures in the fresco, as figures in dreams, are not portraits."

It was an apparent reference to the phrase, "God Does Not Exist," a quote attributed to Juarez adviser Ignacio Ramirez and written on a piece of paper by Ramirez in the mural.

Eight years after the mural was completed, Rivera changed the paper to read, "Conference in the Academy of Letran, the year 1836." The phrase refers to the date and place where Ramirez made his controversial comment.