Emperor Nero participated in the Panhellenic Games in 67 AD, and Isthmia was on his circuit. This is the same man who had his own mother murdered, who fiddled (possibly) while Rome burned, and who later declared himself a victor in competitions he ordered held in his honor. At these games - second in prestige only to Olympia - victors received crowns of wild celery leaves (not laurel, not olive: celery). The contrast between imperial grandeur and a celery crown is either profound or hilarious. Inside the Isthmia Archaeological Museum, locate any reference to the 1st-century AD games in the late Roman period exhibit. Note the celery wreath descriptions - ask the site attendant to point out the relevant display if you can't find it. Then walk to the stadium area (a short walk from the temple) where those games were physically run.
🔄 BACKUP: The JV Wanderings visitor guide documents all exhibit highlights - read it before visiting to know exactly which cases to look for.