Other mounds a' comin'

Recall I am looking to see what other kinds of mid-to-large sized stone mounds are out there besides rectangular piles with hollows. As previews, here is a fine mound from a few miles northwest of Wachusett:
[No hollows, circular, and mounded up pretty high]

Here is an example from Patch Hill in Boxborough:
[Yes rectangular but no hollows. Also a deliberate use of quartz adds another characteristic.]