Context: Because it was designated as the national capital, many structures were built around that time. Even today, some of them still remain which are open to tourists.

Question: What was the designation of Nanjing?
Answer: the national capital

Question: What happened around the time that Nanjing was designated as the capital?
Answer: many structures were built

Question: Are any of the structures that were built at that time still around?
Answer: some of them still remain

Question: The structures that still remain are open to whom?
Answer: tourists