A ground nozzle is a spray nozzle made for being installed at grade level (i.e. in the ground), usually in cement, crumb rubber, rubberized cement, or a similar nonslip surface, or under a grille or similar opening that is flush with ground level.
Ground nozzles are often arranged along walkways, public spaces, in parks, and the like, for architectural decoration, noise masking in urban settings, and as waterplay areas for people to cool off in on hot days.
References
Ground nozzle Wikipedia(Text) CC BY-SA