As high-rise construction in San Francisco has stalled during the economic downturn, most residents likely view the empty lots left behind as eyesores full of trash, graffiti and weeds.
But when landscape architect Sarah Kuehl passes such spaces, she sees the physical manifestation of the passage of time.
So when she and three other local architects were asked to submit ideas for transforming an empty lot at 399 Fremont St. into a temporary beautification project, they decided to use nature to mark time instead of urban decay.
"We wanted to set up a situation where different things might transform in different ways," group member Adam Greenspan said.
Experts say numerous high-rise building plans have been on hold for years due to the recession, and it could be a decade before some projects resume-- if they ever do.
San Francisco has 5,299 vacant lots that take up 250 acres of space, according to the San Francisco Planning and Urban Research Association.
In July, the San Francisco Chronicle asked three teams to create unofficial proposals for vacant lots across the city, and the newspaper featured the designs last summer.
Today, the Fremont Street team presented their design and explained the thought process behind their proposal as part of a series of discussions about empty lots hosted by SPUR.
The Fremont Street team proposed grading the lot into a hilly terrain that would be visible at street level, then covering it with grass and laying giant crane booms parallel to the ground.
They were inspired by the idea of giant objects at rest, and they thought about all the cranes that have gone still since the construction projects across the city were halted.
Their design also featured a birdhouse wall to keep trespassers out and an assortment of differently sized birdhouses hanging from the cranes in order to attract a variety of species.
The bird park would become more beautiful as time passed, the team explained, as birds gathered and plants grew over the structures.
Although the lot would not be open to the public, "It allows people to think about possibilities and adds to the streetscape," Greenspan said.
The design was simply an intellectual exercise meant to inspire and interest the community, and it appears no such projects have been sanctioned in the city.
Private developers are reluctant to allow their empty lots to be transformed in part because supposedly temporary projects sometimes become permanent - such as the Eiffel Tower in Paris and Palace of Fine Arts in San Francisco.
No company wants the bad press associated with tearing down the beloved community garden once the development project is finally back on track, the group members explained.
But this "problem of permanence" doesn't have to be a given, group member Owen Kennerly said. Temporary projects that move, or whose removals can be an event in and of themselves, are ideal, he said.
Plus, permanent projects require years of permitting and development, while, "Temporary projects let you try ideas and see if they take hold," Kennerly said.
The group considered hot-air balloons that would move up and down on their own as the temperature changed, which could be moved or released when the high-rise was ready to be built.
They also thought about Burning Man and the idea of building a wooden structure whose purpose would be to be destroyed or dismantled later.
Other temporary project ideas included cover crops, worm farms that would produce soil, or space for trees to be grown in containers and later moved.
"Companies could actually score a marketing coup if they made the coming-down a festival or celebration," Kennerly said.
Mayor Gavin Newsom's Office of Economic and Workforce Development is working on protocols and incentives to encourage developers to allow temporary installations in the empty lots, according to the design team.