Largest exercise demonstration / class (multiple venues)

According to Official Guinness Records,

On 27 September 2003 in Kazakhstan a total of 4,845,098 people across the country took part in the largest ever simultaneous aerobics display in an attempt, supported by Kazakhstan's Presidential administration, to promote a healthy lifestyle.
The participants amounted to approximately 30% of the total population. All participants followed the same routine, the music for which was broadcast by Kazakh radio across the country.

For a complete list of 2003 records, please visit 2003 Guinness Records in Kazakhstan.

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• Most powerful rocket
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• Largest crater from an underground nuclear explosion
• Worst space disaster - ground death toll
• First artificial satellite