The Latin motto is from the Bible, 1 Chronicles 29:
Dies nostri quasi umbra super terram et nulla est mora.
Our days on the earth are as a shadow, and there is none abiding.What an apt motto for a sundial where the shadow moves ever onward without delay!
I found this image at Wikimedia Commons (thanks to Rj1979), and I also found a wonderful photo gallery, including historical photographs from the time of the sundial's installation, at the Gnomonika website.
Here is the sundial, and the zodiac symbols can be seen up and down to the left and the right; click here for a larger image that shows the zodiac signs in detail.