Clicking the locators on the map provides you with info about that particular site, about which HGblog contains information. Links for further reading can be found there as well.
Clicking the link under the map will provide you with a larger map with in the left side bar an overview of gardens featured on this map, links and more information. All images you may find there are courtesy of the people who have joined and participate in the Historical Gardens group on flickr, where photos of historical gardens and parks are gathered. Please be aware that normal copyright restrictions are in place, unless specifically stated otherwise. These restrictions may vary from picture to picture.
You can add photographs of your own to the pool, but you will need to get yourselves a flickr account if you want to do that. Please do. You are invited to share.