What were the circumstances immediately before and after the Buddha’s Nibbana?
The Buddha had been very sick when in Vesali. After the Rainy Season Retreat (Vassa) in Vesali he went with his disciples towards the northwest. On the way he had food offered by the blacksmith Cunda and became seriously ill. Finally he reached the bank of a river in Kusinara. After taking a bath he lay on his right side with his head resting on his right hand, on a hammock placed among four pairs of sala trees. Subsequently, all the recumbent (Sleeping) Buddha statues or the statues of the Buddha’s Nibbana have been modeled in this posture. The Buddha informed his disciples of the approach of his Nibbana, and all his disciples watched over him. At night, a Brahmin scholar named Subhadda came to see the Buddha. When Ananda tried to stop him, the Buddha called Subhadda to his bedside and preached a discourse for him, so Subhadda became the last disciple of the Buddha’s lifetime. From the time he left Vesali on the journey, the Buddha preached to his disciples many times and at midnight when he was about to die, he told them for the last time, “You should not think that you no longer have a teacher. Rather you should regard the teachings (Dhamma) as your teacher. Be diligent in striving for salvation. Never be indolent.”
After the Buddha’s death, his body was cremated. The remains were divided into eight portions by Magadha, the Sakya, and other states and then enshrined in thupas constructed in the eight states. By the 3rdcentury BC a portion of the Buddha’s Sarira enshrined in Buddhagaya in Magadha was taken out by Kong Asoka and was divided into many portions to be stored in thupas in different places. In 1898, archeologists discovered a Sarira thupa on the southern border of Nepal when they excavated an ancient location of Kapilavatthu. Inside the thupa they found stone vases, urns and other articles. One of the vases was kept in an urn made of layers of iron and crystal. In the vase there was a golden flower with the Buddha’s bones placed on it. The inscription on the urn indicates that this is the Buddha’s Sarira enshrined by the Sakyas.（From Essentials of Buddhism: Questions and Answers）