Bain News Service,, publisher.
6000 girls at Sokol Sports at Prague, Austria
[1912]
1 negative : glass ; 5 x 7 in. or smaller.
Notes:
Title from data provided by the Bain News Service on the negative.
Photo shows young women standing in formation, probably during the 6th Sokol Slet (gymnastic festival) held in 1912 in Prague (then part of the Austro-Hungarian Empire, now located in the Czech Republic). (Source: Flickr Commons project, 2008)
Forms part of: George Grantham Bain Collection (Library of Congress).
Format: Glass negatives.
Rights Info: No known restrictions on publication.
Repository: Library of Congress, Prints and Photographs Division, Washington, D.C. 20540 USA, hdl.loc.gov/loc.pnp/pp.print
General information about the Bain Collection is available at hdl.loc.gov/loc.pnp/pp.ggbain
Persistent URL: hdl.loc.gov/loc.pnp/ggbain.11569
Call Number: LC-B2- 2521-14

What a treasure !!
There is a Wikipedia article on Sokol, which was the Czech version of the German Turnverein and other such youth athletic organizations which were part of a late 19th century mania for physical culture.
The mass gatherings were called Slets, and are still held today. Here you can see one Flickr user’s photos tagged with sokol. You can also Google "sokol slet" to find a YouTube video promoting the 2009 Sokol Slet to be held in Fort Worth, Texas.