Traveling to Spain in August

I am going to Spain for the first time in August 19th to 30th. I am flying to Barcelona and I was planning on Valencia as well. I don't know if anyone has any tips on things to do and discover the city. I don't like to do touristy things but I would love to discover more the architecture the art, the food and meet locals and expats that live there and go out for drinks. I have been wanting to go for so long so finally I am making it. I would appreciate any advice.