Q: This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
The Romans liked bright colors, and many Roman villas were decorated with vivid red murals. The pigment used for many of the murals was called vermilion, and it came from the mineral cinnabar, a common ore of mercury. It was one of the finest reds of ancient times the paintings have retained their brightness for more than twenty centuries. The source of cinnabar for the Romans was a group of mines near Almaden, southwest of Madrid, in Spain. Working in the mines was extremely dangerous, since mercury is highly toxic; the miners were slaves or prisoners, and being sent to the cinnabar mines was a virtual death sentence.
A:
What pigment was used to paint villas in ancient Rome?