Which Olympics in the modern era were the 1st to hold Opening Ceremonies?

1908 - London, England

The 1908 Olympic Games were originally scheduled to be hosted by Rome, but the 1906 eruption of Mount Vesuvius caused the Games to be relocated to London.

These Games were much better organized than the previous regularly scheduled Olympic Games (they were even the first to have an opening ceremony), yet they were marred by politics and nationalism. Britain's recent refusal to give Ireland its independence caused Irish athletes to boycott the Games and caused contestants from the U.S to not dip the American flag to the British royalty during the opening ceremony (a tradition the U.S. continues to this day).

There was also controversy over the 400-meter final heat. As four runners came into the final stretch, W.C. Robbins (U.S.) was first, followed by J.C. Carpenter (U.S.), with British Wyndham Halswelle coming in third, and followed by a fourth runner from the U.S. As Carpenter and Halswelle (second and third runners) swung out to pass Robbins, someone shouted "Foul!" Though Carpenter (the U.S. runner who had been in second) finished first, with Robbins (U.S.) in second, and Halswelle (U.K.) in third, the British officials accused Carpenter of blocking and elbowing Halswelle and voided the whole race. The race was ordered to be rerun, but since the American runners refused to redo the race, Halswelle ran the race all by himself to win the gold.

It was in the 1908 Olympic Games that the exact distance of a marathon was established as 26 miles and 365 yards. Diving was added to the events for this year.

Approximately 2,000 athletes participated, representing 22 countries.

I'm only guessing but the modern era began in 1896 in Athens, Greece, so I'll say it was then.

Barcelona 1992, it was a piece of art.