Context: The cathedral has a heliometer (solar "observatory") of 1690, one of a number built in Italy in the 17th and 18th centuries. The device itself is quite simple: a tiny hole in one of the minor domes acts as pinhole camera, projecting an image of the sun onto the floor at solar noon (12:00 in winter, 13:00 in summer). There is a bronze line, la Meridiana on the floor, running precisely N/S. The ends of the line mark the positions as at the summer and winter solstices; signs of the zodiac show the various other dates throughout the year.

Question: What is a heliometer?
Answer: solar "observatory"

Question: What name is given to the bronze line on the floor of a heliometer?
Answer: la Meridiana

Question: Which direction does la Meridiana run?
Answer: precisely N/S

Question: What image is projected on the floor of the heliometer?
Answer: the sun

Question: What has lunar observatory built in 1690?
Answer: Unanswerable

Question: was built in the 16th century?
Answer: Unanswerable

Question: What is the name of the gold line on the floor of a helimeter?
Answer: Unanswerable

Question: What image is projected onto the dome of the heliometer?
Answer: Unanswerable

Question: What signs are a tribute to pagean customs?
Answer: Unanswerable