A sidewalk drain, one section on the pavement, and the other part with the drain openings located at the foot of the sidewalk.
GS - Spheroidal graphite cast iron - a special cast iron in which the crystallization of carbon has been slowed down, which makes it close to steel - also called ductile iron (Thanks to Vuori Susi for the clarification)
The lid is similar to another manhole cover made by the same manufacturer