“最... ...的之一” for example“最漂亮的女孩之一”means “one of the most beautiful girl” “One of the most beautiful gardens in China”意思是"中国最漂亮的花园之一"

'One of the most beautiful gardens in China'→（中国最美丽的花园之一） one of the most 最....的之一 if you want to say something about 'one of the most'. you could accept to change "one of the most adjective + noun " to "最 adjective 的noun之一"

中国最美的花园之一。 最 most 美 beautiful Check out this article for how to use the "zui4" superlative: https://resources.allsetlearning.com/chinese/grammar/Superlative_%22zui%22