was there an opening ceremony conducted?
Yes
1896 Summer Olympics
On 6 April (25 March according to the Julian calendar then in use in Greece), the games of the First Olympiad were officially opened; it was Easter Monday for both the Western and Eastern Christian Churches and the anniversary of Greece's independence. 
who took part in the modern olympic games Fourteen nations; all European, and 241 athletes (all males) when was this? From 6 to 15 April 1896 where did it take place? Athens, Greece which were the venues? Panathenaic Stadium, Marathon, Bay of Zea, Zappeion, Kallithea, and Athens Lawn Tennis Club
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1896 Summer Olympics [SEP] Opening ceremony
On 6 April (25 March according to the Julian calendar then in use in Greece), the games of the First Olympiad were officially opened; it was Easter Monday for both the Western and Eastern Christian Churches and the anniversary of Greece's independence. The Panathenaic Stadium was filled with an estimated 80,000 spectators, including King George I of Greece, his wife Olga, and their sons. Most of the competing athletes were aligned on the infield, grouped by nation. After a speech by the president of the organising committee, Crown Prince Constantine, his father officially opened the Games with the words (in Greek): "I declare the opening of the first international Olympic Games in Athens.