How can I find the 'pictures' folder on my iMac?

I scanned a couple of documents using the 'image capture' app, and the images appear to be saved in 'pictures' ....but I can't find that folder. When I open 'Finder' neither 'pictures'. nor for that matter 'Photos' are there. But when I was searching trying to find the images of the documents I'd scanned (I never did find them) I came across loads of photographs that do not feature in 'Photos' when I open it. Some of them are old photos that I recognise, some of them...I have no idea what they are or where they came from. They seem to show in Preview, but I have no idea where they are on the computer, or how to get back to them or how to manage them. Any ideas? Thanks.