Should I say ‘it’ or ‘that mountain,’ ‘it’ or ‘such a mountain’ in the sentences?

Should I say ‘it’ or ‘that mountain,’ ‘it’ or ‘such a mountain’ in the sentences? My personal choices are the second ones, but are these correct?

It was mid-morning when Terence arrived at Mount Fujiyama in Japan. No ethnic people were living in (it, that mountain). When his boss gave him a new assignment in Asia, he knew that (it, such a mountain) was the best setting for his new research.