Beaucoup de

Bonjour Richard,

"There were many obstacles and (some) climbing walls"

 I have copied the text above from the story preview.

I find it interesting that the author has chosen to include closed brackets around the word "some".

I see this as a hint to use the indefinite article "des" to express "some" 

Therefore, we have "des murs d'escalade"   -->  there were some climbing walls.

I hope that I have understood your query correctly.

Bonne journée

Jim