The prize at the Isthmian Games was a wild celery or pine crown*.
The isthmus of the games lies between the Saronic and Corinthian Gulfs.
The Isthmian Games were established in 582 B.C. [Neil Asher Silberman, John K. Papadopoulos, Ian Morris, H. A. Shapiro, Mark D. Stansbury-O'Donnell, Frank Holt, Timothy E. Gregory "Greece" The Oxford Companion to Archaeology. Brian M. Fagan, ed., Oxford University Press 1996.]
*"The Isthmian Victory Crown," by Oscar Broneer. American Journal of Archaeology, Vol. 66, No. 3. (Jul., 1962), pp. 259-263.