POPOS are plazas, terraces and small parks that dot downtown San Francisco.
"I have a map; I keep it on my desktop and if I have time, I visit one for lunch," Ted Kuster said.
One POPO Kuster recently enjoyed is an oasis on the roof of the Mechanics Bank building in the Financial District. There is a plaque on the outside of the building inviting you up.
There are signs for all the privately owned public open spaces, but you have to know where to look.
"I don't want to say they have deliberately tried to hide the spaces, but if you go around the downtown area it's hard to find the spaces and we just want to make it easier for the public," San Francisco Supervisor David Chiu said.
Chiu is working on a measure to increase the size and improve the placement of the welcome signs.
Since 1985, city law has required downtown developers to include these spaces and they are responsible for the upkeep. The building owners and managers association says current properties should not be affected by any new city mandates.
"If they want to put more new rules on how you advertize these privately owned publicly accessible spaces, that's something for new projects down the road, but don't change the rules as they were approved already for existing buildings," Ken Cleaveland of the Building Owners and Managers Association said.
The issue of POPOS was addressed in a 2009 report by the San Francisco Planning and Urban Research Association, which counted 68 of what it calls the "city's best kept secrets."
"The way they function as public spaces is only as good as people utilize them, so if no one knows about them and no one talks about them, they don't serve their intended purpose," SPUR spokesperson Sarah Karlinsky said.