To see all of a site's content in one location, navigate to the site and click the Content tab. Here you'll see all the site's pages, albums and events listed. You can browse the content, search or sort and filter by content type, page type, page category, author name or published date. For events, you can filter by event date.
As a Content manager, Site manager/owner or App manager, you can head to your user menu and click Manage > Content to manage all content you own or manage.