Running has always been a unique test of the physical and mental ability of the human race. Early humans ran and chased down their prey to be able to eat, and this is where we as a race began to develop our ability to run long distances. Oftentimes, people were not fast enough to run down an animal in the sprint. The only way for us to catch something that we were chasing was to run after it long enough that it would eventually give in to its fatigue.
Running also has its place in Roman history with a messenger named Pheidippides. The story is that he ran from Marathon to Athens to announce that the Persians had been defeated. The distance that Pheidippides had to run was roughly 25 to 26 miles. Sadly, after he was able to relay the information he died from exhaustion.
This story is the inspiration for the marathon race that so many people now take part in. The marathon is a unique test of our abilities, 26.2 miles of pounding on the body. In 1908 at the Olympics games in London England 2.2 miles were added to the original course so that the race would end in front of the royal's family's box. The distance has not changed since that day and continues to be 26.2 miles of running.
Many people now consider the marathon to be the holy grail of running. It doesn't matter how fast you run it, or how many times you have run one. I tend to agree that the marathon is the highest regarded task for any runner. I've never run a marathon. However, I have run a half marathon and the experience of finishing was a great one. I can only imagine that it would be amazing to finish a marathon.
Athens holds a marathon once a year, and it said that it follows the original path that was taken by Pheidippides. Therefore, allowing you to follow in the footsteps of someone who was very important to the history of running. Without him we may have never come up with the idea for the marathon, and thus we would lack one of highest regarded accomplishment for many runners.
If you aren't a runner I would advise taking it up. Running is a great way to support your health, and fitness. You don't have to run a marathon to enjoy running. There is many other accomplishment that you can be proud of.