Before the Piedmont Hotel was built, Mark Twain visited the Piedmont Springs while on a lecture tour in Oakland in 1868. Photographer Eadweard Muybridge recorded this visit in front of the gazebo-covered spring. Twain is holding a cup of mineral water. The restored faux grotto in Piedmont Park is located at the spot where Mark Twain was once photographed. The lower grotto was built on the site of the original wood gazebo.
From the article on patch.com
By Charles Burress, Patch Staff
Posted Tue, Feb 12, 2013 at 10:42 pm
This historic photograph shows a young Mark Twain in top hat signing autographs at Piedmont White Sulphur Springs in 1867. We're asking readers to help us pinpoint exactly where it was taken. Do you know?
In 1867, famous English photographer Eadweard Muybridge photographed famous American writer Mark Twain at "Piedmont White Sulphur Springs."
The photo, from the Joseph R. Knowland collection of the Oakland History Room at the Oakland Public Library, shows Twain in top hat signing autographs. An arrow pointing to Twain was added by graphic artists at the Oakland Tribune, according to library records.
Muybridge is perhaps best remembered for his successive-frame photography capturing human and animal movement, and is credited with proving that a running horse can have all four hooves in the air at once.
Additional information here
Another picture of the gazebo at Piedmont Springs:
Oakland Pioneers History - Mark Twain Quote about Piedmont - Oakland Tribune - Sunday, July 12, 1925:
Mark Twain was prominent at a picnic gathering Piedmont Springs, now "the city without a business house," and Bret Harte, Joaquin Miller, Jack London, Ina Coolbrith and other literary celebrities contributed to the fame of Oakland.