Gaya is the answer that matches the Bihar-specific fact asked in the question. The Barabar Caves are located in the Jehanabad/Gaya district of Bihar (the caves are administratively linked to Jehanabad but are geographically close to Gaya). They are the oldest surviving rock-cut caves in India, dating back to the Mauryan period (3rd century BCE), constructed during the reign of Emperor Ashoka. The Barabar hill group has four caves: Lomas Rishi, Sudama, Visvakarma, and Karan Chaupar. The Nagarjuni Hills nearby also have three more caves. Forster based his fictional Marabar Caves in the novel 'A Passage to India' on the Barabar Caves. Nalanda district is famous for the ancient university ruins and is a UNESCO World Heritage Site. Rohtas district in south Bihar is known for the Rohtas Fort and Rohtasgarh, but not the Barabar Caves. Jamui is a district in south Bihar with tribal heritage but has no connection with the Barabar Caves. These caves are an important ASI-protected monument and a rare example of Mauryan rock-cut architecture. Bihar GK questions frequently place neighbouring districts, rivers, historical centres, personalities or government institutions together as distractors, so recognition of a familiar name alone is insufficient. The alternatives Nalanda, Rohtas, Jamui may be valid Bihar-related terms, but they do not satisfy the complete relationship asked here. Revise the complete pair ‘The Barabar.