Problem: What are the most important words?
a city has been a place of worship and prayer for centuries .
Answer: place, prayer, worship

Problem: What are the most important words?
railway bridge across the canal with a large skyscraper in the distance
Answer: bridge, canal, skyscraper

Problem: What are the most important words?
barge carrying rubbish along river in winter
Answer:
barge, carry, river, rubbish