With SharePoint 2013, How do we create sitemap of a sub site OOTB?
In sharepoint 2013, we have native support for generating xml sitemaps which was not present in the earlier versions of sharepoint. Sitemaps basically inform the search engines about the pages and their metadata, present in your site. This help the crawlers in picking up those pages. This is a great feature especially for public facing websites. see this https://mysharepointlearnings.wordpress.com/2013/10/20/sitemaps-in-sharepoint-2013/
TOC web part (publishing infrastructure). Configure it to pull from whatever subsite you want.
You can also use the Content Query web part and tell it to get the Pages content type from your subsite.
Or, for a more robust solution, the Content Search (if search is enabled) web part. Set the scope to Site.URL and contentclass: STS_web. You can configure this via the settings options for the web part.