I was reading this article and there are a couple of spots that I don't understand when it comes the grammar.
専門家は「雄と雌の体を持ったカブトムシが生きているところを見たのは初めてです」と話しています。
Roughly: The specialist said 'It is the first time I have seen a beetle that has a male and female body'
Why/What is the purpose of the bolded の? Why does it comes after 見た? の particles that look like this come up a few times in the article actually