GALLERY: Muddy fun at Poland's Woodstock festival

In August 1969, the Woodstock Music & Art Fair took place on a dairy farm in Bethel, NY. Over half a million people came to a 600-acre farm to hear 32 acts (leading and emerging performers of the time) play over the course of four days (August 15-18). Jefferson Airplane, Jimi Hendrix, the Grateful Dead, the Who, Janis Joplin and Crosby, Stills, Nash & Young were among the line-up. Woodstock is known as one of the greatest happenings of all time and –perhaps- the most pivotal moment in music history. - See more at: http://woodstock.com/about/#sthash.fpYoJ5kw.dpuf

Have a rolling good time... in the mud.

That's what more than 750,000 people did at this year's Woodstock Festival in Poland's Kostrzyn-upon-Odra, near the Polish-German border, NBC News reported.

The Woodstock festival was initiated by Polish journalist and social campaigner Jerzy Owsiak 20 years ago as a way of thanking those who donated to his charity.

It gives medical care to children suffering from kidney diseases.

The free festival takes its inspiration from one of the most pivotal moments in music history, the 1969 Woodstock Music & Art Fair.

It unfolded over three days, from Aug 2 to Aug 5.

Here are some highlights.

Photos: Reuters

Sources: Reuters, NBC News, Woodstock