The opening scene of the opera is laid at Memphis, a fact which justifies the utmost grandeur in the stage furniture, and is explained by Mariette's interest in that place. It was he who helped moderns to realize the ancient magnificence of the city described by Diodorus. It was the first capital of the united kingdom of upper and lower Egypt, the chief seat of religion and learning, the site of the temples of Ptah, Isis, Serapis, Phra, and the sacred bull Apis. Mariette here, on his first visit to Egypt, unearthed an entire avenue of sphinxes leading to the Serapeum, over four thousand statues, reliefs, and inscriptions, eight gigantic sculptures, and many other evidences of a supremely great city. He chose his scenes with a view to an exhibition of the ancient grandeur. In a hall of the Royal Palace, flanked by a colonnade with statues and flowering shrubs, and commanding a view of the city's palaces and temples and the pyramids, Radames, an Egyptian soldier, and Ramfis, a high priest, discuss a report that the Ethiopians are in revolt in the valley of the Nile, and that Thebes is threatened. The high priest has consulted Isis, and the goddess has designated who shall be the leader of Egypt's army against the rebels. An inspiring thought comes into the mind of Radames. What if he should be the leader singled out to crush the rebellion, and be received in triumph on his return? A consummation devoutly to be wished, not for his own glory alone, but for the sake of his love, Aïda, whose beauty he sings in a romance ("Celeste Aïda") of exquisite loveliness and exaltation. Amneris, the daughter of the King of Egypt (Mariette gives him no name, and so avoids possible historical complications), enters. She is in love with Radames, and eager to know what it is that has so illumined his visage with joy. He tells her of his ambition, but hesitates when she asks him if no gentler dream had tenanted his heart. Aïda approaches, and the perturbation of her lover is observed by Amneris, who affects love for her slave (for such Aïda is), welcomes her as a sister, and bids her tell the cause of her grief. Aïda is the daughter of Ethiopia's king; but she would have the princess believe that her tears are caused by anxiety for Egypt's safety. The King appears with Ramfis and a royal retinue, and learns from a messenger that the Ethiopians have invaded Egypt and, under their king, Amonasro, are marching on Thebes. The King announces that Isis has chosen Radames to be the leader of Egypt's hosts. Amneris places the royal banner in his eager hand, and to the sounds of a patriotic march he is led away to the temple of Ptah (the Egyptian Vulcan), there to receive his consecrated armor and arms. "Return a victor!" shout the hosts, and Aïda, carried away by her love, joins in the cry; but, left alone, she reproaches herself for impiousness in uttering words which imply a wish for the destruction of her country, her father, and her kinsmen.