WATCH: Urban Forest Erupts in San Francisco's Edgy Tenderloin

The "Tenderloin National Forest" is likely one of the world's smallest "forests" -- it's just 23 feet wide by 136 feet deep -- but it is a refuge in one of the most densely-packed neighborhoods in the heart of San Francisco.

When artists Darryl Smith and Laurie Lazer first moved into a space on Cohen Alley in 1989, it was "a place emblazed in a health-hazardous cesspool of bodily fluids and other dumped items, non-supervised open-air chemical experiments and illicit criminal activities".

In 1990, Smith planted a 12 foot redwood that "didn't look like it was going to make it, actually, it felt like we'd committed a crime against nature". Later, they brought in more trees, built a wood-burning oven (that the fire department later deemed safe for their community cookouts), added murals to the walls, hand-crafted stone floors and a tiny, wattle-and-daub shed.

Today, Smith's Luggage Store Gallery pays $1 per year to lease the property from the city, provided they keep it open to the public 20 hours per month. Anyone can come garden here (there are tools in the earthen hut) and a few times a month they bake things like pizzas, breads and yams in the traditional "horno".

Watch Kirsten's feature-length documentary on tiny homes, "We the Tiny House People: Small Homes, Tiny Flats & Wee Shelters in the Old and New World."