Hidden San Francisco: SoMa's sinking houses

SAN FRANCISCO -- In San Francisco's South of Market neighborhood, there's a mystery hiding in plain sight: old homes that are quite literally sinking into the soil.

It all started after the 1906 earthquake. More than a century later, some of the neighborhood's older homes sit nearly six feet below street level.

Check out the video above to find out why.

Hidden San Francisco is an exclusive ABC7 series uncovering secrets of San Francisco. Click here to watch more stories.