Describe a setting, fictional or non-fictional, by simply imagining it and then sharing your vision in 150 words or less. Then find a similar setting in real-life, study it carefully, and describe it, again sharing your vision in 150 words or less. The descriptions can be detailed, or metaphorical, or evocative, or whatever style you choose, and they need not both use the same style. The objective is to explore the differences (if any) between working from a mental picture and working from reality, as well as flexing your powers of observation.
For those who want to share their efforts at the meeting, the other members will hear both, and try to guess which one came from the mind and which was observed, and why they thought so.