On 29 April 2017 , explorers will run .
On 29 April 2017 , explorers walk over and under 6 , 11 , 22 or 33 km of landscape that has to be seen to be believed .
On 29 April 2017 , explorers will run or walk over and under 6 , 11 , 22 or 33 km of landscape that has to be seen to be believed .