Here are some hidden gems in San Francisco:

1.     The Wave Organ: Located in the San Francisco Bay, this installation is a structure that creates various sounds from the sea waves, resembling an organ.

2.     Balmy Alley Murals: This street, situated in the Mission district, is filled with vibrant wall murals. These artworks focus on societal issues and represent the city's underground art scene.

3.     Seward Street Slides: These slides are designed not for children but rather for adults. Located in Eureka Valley, this hidden spot offers a different entertainment experience.

4.     Mosaic Staircase: Near Golden Gate Park, these stairs are adorned with colorful mosaics and provide a unique backdrop to the cityscape.

5.     Clarion Alley: This street in the Mission district is famous for its ever-changing wall murals. The artworks focus on the cultural diversity of San Francisco.

6.     Tiled Steps of 16th Avenue: These colorful mosaic stairs are in a unique position to observe the city from above. They are located near Golden Gate Park.

7.     Museum of the African Diaspora (MoAD): Celebrating the cultural heritage of the African diaspora, this museum is often considered a less-known gem.

8.     Hidden Garden Steps: Located in the Inner Sunset area, these steps are adorned with colorful mosaics, offering a different artistic perspective of the city.

Keep in mind that some of these places may require reservations or have specific visiting hours, so make sure to check if the places you plan to visit are open and comply with any conditions.