- Go to https://www.google.com/takeout/
- Select Choose services, then Picasa Web Albums
- Click on Configure, Download a single album
- Select the album you want, then Create Archive
- Note: it's not instant, the archive takes a while to create. When it's done, it's kept for a few days so you can download it.
I'm trying to figure out: since Picasa doesn't download existing photos on your computer when you download an album, the downloaded folder won't have all your photos. How can I see/export all my photos in one place?