Among the many paintings by Raphael in the room, I suggest starting with his last work, the Transfiguration. This great altarpiece actually depicts two different episodes: below you can see the Apostles trying in vain to heal a possessed boy; above, on the summit of Mount Tabor, you can see Christ rising up into the air wrapped in white robes between the prophets Moses and Elijah. Despite the difficulty of connecting the two different situations, the painting is fluid and homogeneous, and loaded with emotions and reciprocal references. Only a few brush strokes were missing from the painting when Raphael died early at the young age of 37, leaving an immense void in Renaissance art.
FUN FACT: when Raphael died in 1520, the painting Transfiguration was placed near his funeral bed. The public interest for his latest work was so strong that to print multiple copies, they used one of Raphael's preparatory drawings where all the characters appeared naked.