Final answer:
The building feature that sheds water and gives a unique shape to buildings is the dome, an architectural element derived from the rotation of an arch around a central point, best exemplified by the Pantheon in Rome.
Step-by-step explanation:
The feature that sheds water and gives a unique shape to buildings is the dome. This architectural element is created by rotating an arch around a single point, subsequently forming a large hemispherical structure that can cover expansive interiors. Not only does the dome provide an elegant silhouette to a building, but it also has structural advantages. Domes are often found atop important buildings and were key in Roman architecture. The Romans were masters at manipulating the arch to create massive, open interior spaces free from columns or other supports, like the coffered concrete dome of the Pantheon. Therefore, the correct answer to the question is b) Dome.