Discover the beautiful blue grotto (where the witches may live).
It's commercial alright but there's no doubting how pretty the iridescent blue water of the grotto is, and the trip there is fun too. Discovered in the time of Tiberius, the place was initially thought to be haunted by evil spirits and so was avoided; it was rediscovered in the 19th century and since then has become one of Capri's most popular attractions. When the weather is fine a small rowing boat will take you into the grotto (you'll need to lie down in the boat as the opening is very narrow) and, thanks to reflecting sunlight, the water appears to take on the colour of sky. If you're lucky, your boatman might even sing you a song so that you can experience the wonderful acoustics.
The grotto is about 10 minutes by boat from Marina Grande.