Here are suitable relative pronouns/adverbs for the blanks:

1. They stayed at a hotel **whose** rooms offered breathtaking views of the city.
2. We met a friendly local guide **whose** knowledge of the area was impressive.
3. The hotel receptionist **who** spoke multiple languages helped us with directions.
4. The destination **that** he chose for his next holiday is abroad.
5. The homestay **whose** host used to be a tour guide is very well-designed.
6. We stopped to explore an old village **where** there are many ancient houses and farming tools.
7. The travel agency **that** provided us with the tour gave us a small discount.
8. People can use online apps to book tickets and accommodation, **which** is so convenient for visitors.
9. The hotel **that** was located near the beach offered stunning ocean views.
10. They plan to visit Paris, **where** the Eiffel Tower is world-famous.