Indeed

When you look at how far we've come as humans, when you consider that we've developed something called civilization, you come to realize that the finest evidence of our civilization is the city. The city is a symbol of experimentation and creation, a place where we can come together for work and entertainment, for art and culture, for wonder and opportunity. And, like the rural villages of the past, the city is where we come together to share cultural experiences with other humans - indeed, to define what it is to be human.

(Hello! How do I get "indeed" in this context? There's a couple of definitions for this word in the dictionary. But I still do not figure out which definition is suitable for this sentence! Could you have a look for me? If you can offer me a simliar example, I think that would be clearer and simpler for me to get it. Thanks in advance! )