Idea's needed from creative thinkers

[Esther]

I am planning an Amazing Race type event and would like some thoughts on "task" to complete.

Remember it is only a 1 day event and have a cut off of 1,000 racers. Could have as many as 50 - 75 people at one place to complete a task, depending on the difficulty of the task.

I want it difficult enough to not be boring but not so hard that you want to give up.

Some suggestions I have seen are doing puzzles like sudoku.

I was thinking if I could find a paint ball location that would be fun.

Any suggestions?