"Where is the hospital?"
Na er is a northern accent. Na li is used more throughout china but people will understand you either way
What's the difference between 'where is the hospital?' and 'the hospital is there.' ? Both are 医院在哪儿, right?
The two "na" characters are different. 那 means there, whereas 哪 means where. The little box makes a difference
哪裡(trad.)/哪里(simp.) is another way to express "where" and interchangeable with "哪兒/哪儿", but the former is more formal.