The NN Zevenheuvelenloop, also known as the nation's most beautiful and the world's fastest 15 kilometer race this year.The NN Zevenheuvelenloop has undergone a lot of development in the past 32 years.From a 'walk' with 500 men has grown into an event where almost 40,000 people register for it.This makes it the largest 15km race in the world and with the world record for men also the fastest in the world.