Ask HN: Discovering HN type sites for other interests

There have been some interesting articles that pop up here from time to time that are outside the technical focus. I often find them interesting and enlightening - especially some of the archaeological related ones.

That said, a non-tech person I sometimes send some of those articles to was asking me if I knew of or how to find sites that have some of the same traits - high quality submissions, an active audience - for other areas.

For instance - history, cooking, or plants might be very general areas. It seems like Reddit is a popular spot for such. But any thoughts on discovering high-content sites in other, non-tech, areas?