which were the venues?
Panathenaic Stadium, Marathon, Bay of Zea, Zappeion, Kallithea, and Athens Lawn Tennis Club
1896 Summer Olympics
Panathenaic Stadium was the main venue, hosting four of the nine sports contested. The city of Marathon served as host to the marathon event and the individual road race events. Swimming was held in the Bay of Zea, fencing at the Zappeion, sport shooting at Kallithea, and tennis at the Athens Lawn Tennis Club. Tennis was a sport unfamiliar to Greeks at the time of the 1896 Games.

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
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1896 Summer Olympics [SEP] Venues
Four of the 1896 venues were reused as competition venues for the 2004 Games. The velodrome would be renovated into a football stadium in 1964 and was known as Karaiskakis Stadium. This venue was renovated in 2003 for use as a football venue for the 2004 Games. During the 2004 Games, Panathinaiko Stadium served as host for archery competitions and was the finish line for the athletic marathon event. The city of Marathon itself served as the starting point for both marathon events during the 2004 Games. The Zappeion served as the first home of the organizing committee (ATHOC) for the 2004 Games from 1998 to 1999, and served as the main communications center during those Games.