Otto took many photos of Seattle parks. Leschi Park is at the eastern edge of Seattle, on the shore of Lake Washington.
Mary Frasch appears to be posed in the background with Elsie and Ada, her first two daughters. Note the car driving up the street.
The Yesler Way cable car bridge in the center of the picture still exists, crossing over Lake Washington Boulevard at the tennis court within Leschi Park, near the stub section of E. Yesler Way. There is no record that this stretch of Lake Washington Boulevard was ever named Interlaken Boulevard; the current Interlaken Boulevard ends over two miles north of this spot.
There are multiple images numbered 16:
We don't know why Otto reused the image number so many times.