Thanks once to Flickr user mixtara for pinpointing the location of this photo.
I unfortunately did not write down the slide number. But it sits in the slide carousel after a photo from the Rossiya Hotel looking at Red Square, and before a photo of people waiting in line for Lenin's Tomb.
Photo by my grandfather David C. Cook. Scanned from an unlabeled Kodachrome slide, date stamped June 1969. In slide cartridge labeled "Russia".