Two of San Francisco's Three Natural Lakes

Until yesterday I didn't know that San Francisco had only three natural lakes, and I didn't know what they were.  But when some friends asked me what I'd like to do for my upcoming birthday, I requested a walk to or around Mountain Lake.  Later the friend who took me home agreed to a walk around Stern Grove, and we went to Pine Lake, where we found out that it, like Mountain Lake, was one of three natural lakes in San Francisco.  Here's a link for a  fascinating article on the history of these lakes, their present state, and what's being proposed (and even done in some cases!) to restore them:

http://www.openspacesf.org/node/25

You could probably guess that San Francisco's third natural lake is Lake Merced.