Kovacs thrives amid Zurich's cheers with beers
Kovacs, a two-time former world champion, went out to 23.23 metres with his second attempt at a makeshift arena at Sechselautenplatz, the central city square on the shores of Lake Zurich.
The 33-year-old's effort was just 14cm off the world record set by American teammate Ryan Crouser, the reigning Olympic and world champion finishing second with a best of 22.74m.
Only Crouser has managed to throw further than Kovacs, twice in 2021: for the world record in Eugene in June (23.37m) and to win the Olympic title in Tokyo in August (23.30m).
New Zealand's Tom Walsh, 2017 world champion and fourth in Oregon, rounded out the podium (21.90).
"I've had so many throws this year over 22.80 so I feel I was building and building and it's nice to finally tick the box as a 23m shot putter," Kovacs said, praising the street-style relocation.
"As a shot putter I want to thank World Athletics for using us, we don't take up much space. Any time you have a street competition, we're excited to be part of it.
"Every street competition we try and put on a show, get the people happy, maybe cheers with some beers is a good thing, too!"
Another American, world champion Chase Ealey, dominated the women's competition with a best of 20.19m, ahead of Canada's Sarah Mitton (19.56) and Portugal's Auriol Dongmo (19.46).
Democratising athletics
The men and women's shot put were two of six events to be held in downtown Zurich, with first prizes of $30,000 (30,300 euros) on offer for the winners.
The remaining 26 Diamond League titles will be decided in a second day of competition at the famed Letzigrund Stadium on Thursday.
But the importance of holding events outside traditional track and field stadia was also not lost on World Athletics president Sebastian Coe, who won two Olympic 1,500m gold medals for Britain in 1980 and 1984.
"It's democratising the sport," he said. "It's bringing sport to the people."
Kenya's world championship silver medallist and Commonwealth champion Beatrice Chebet produced a last-gasp sprint to seal victory in the women's 5,000m, raced on a conical 560-metre long track that lopped around Zurich's opera house.
Chebet clocked 14min 31.03sec for the win, 0.49sec ahead of compatriot Margaret Chelimo Kipkemboi, with Ethiopian Gudaf Tsegay in third (14:32.11).
Dutch track star Sifan Hassan, who won double Olympic gold in the 5,000 and 10,000m at the Tokyo Games, came in fifth, more than 6sec off the pace.
The men's 5,000m was claimed by Kenya's Nicholas Kipkorir in 12:59.05 as hot, humid conditions quickly changed as a storm moved in.
Dominic Lobalu, a refugee from South Sudan who lives and trains with Swiss club St Gallen, was outsprinted into second while American Grant Fisher took third.
Italy's Gianmarco Tamberi celebrated his recent wedding by tying up the men's high jump with a best of 2.34m, winning on countback from American JuVaughn Harrison.
World champion Mutaz Essa Barshim of Qatar, who shared Olympic gold with Tamberi in Tokyo, finished sixth and last with a sole clearance at 2.18m.
The women's pole vault went the way of Australia's Nina Kennedy, the Commonwealth champion and world bronze medallist clearing 4.81m for the win ahead of world silver medallist Sandi Morris of the US.