A tiny addition in San Francisco’s Golden Gate Park is getting big attention on the Web. A photo on the neighborhood site Richmondsfblog.com first published a photo of a teeny wooden door that mysteriously appeared at the bottom of a tree with a small, gnome-sized gap.

The door has opened up plenty of interest on the Internet—and spurred visitors to the urban oasis to explore the door that's not on any map. It can be found by searching for the grove of old trees in the park's concourse near the Golden Gate Band Shell between the de Young Museum and the California Academy of Sciences.

Creative theories about how it got there abound—mostly as fanciful as the mystery door itself. An elf? A fairy? A house for a mouse?

Kids and kids at heart weighed in with ideas. As “Dude” joked on the neighborhood website, “It’s a very tiny coffee shop. It’s already played out.”

Another commenter, "Hobbit," suggested, “Looks like a squirrel with a [k]nack for architecture."

Everyone seems to agree, it’s cool.

Over on Twitter, K L ‏@miss_kr15 posted, “I totally dragged my bf to the park & hunted that door down after seeing it in your blog. Seriously the coolest thing ever!”

Allyson E-B ‏@allysoneb added, “My daughter left some candy, when we came back 2 hours later it was gone. Fairies!”

The Editor of RichmondSFBlog, Sarah Bacon, noted to Yahoo News in an email that the tree door has been the site's most popular topic ever. “It’s really captured people's imaginations and has gotten more attention than we ever expected. It's a delightful and magical gift someone gave to the park.”

She added, “We're thrilled by the response to the story—I think it's proof that everyone has a child inside that enjoys whimsy and fantasy. It's these little finds that make our neighborhood so special.”

The little find has inspired lots of speculation, but nobody so far has come forth to take credit for building the opening. The good news: The minidoor won’t be closed down anytime soon.

Acknowledging the interest in the door sized for sprites, Andy Stone, Golden Gate Park's department’s section supervisor, wrote in an email to Yahoo News, "We do not encourage such doors but will leave it in place unless it causes problems."

The tiny tree door is not the first to mysteriously appear in a park. Commenters have pointed out there’s the Elf Tree near Lake Harriet in Minneapolis that also has a tiny door in a living tree. Kids leave messages and candy for the invisible resident.