(CNN)It's not only the world's oldest cross-country horse race but it's also arguably the most difficult.
Since 1874, the Velka Pardubicka Steeplechase (otherwise known as the Grand Pardubice Steeplechase) and its notorious 31 obstacles has been drawing crowds to Pardubice -- 60 miles east of Prague in the Czech Republic.
It is so difficult that, during the 144 years that it's been running, there has never been a race where all horses who started it were able to finish.
The most infamous obstacle of them all -- the so-called Taxi Ditch -- is so demanding that not only are horses not permitted to use it for training, it also doesn't appear in any other race in the world.
Before the jump was adjusted to make the ditch shallower, it was a 1.5 meter high hedge, with a five meter ditch that was two meters deep. Nowadays, while the basic parameters of the fence have not changed, the ditch is now four meters long and one meter deep.
It's also more than just a 6,900m long steeplechase, it's also a cross-country race. While the course is mainly grass, horses also have to run through ploughed fields and negotiate water jumps.
The race isn't without controversy and Brigitte Bardot reportedly organized protests in Pardubice many years ago.
"The Velka and the National are not cemeteries for horses... [It's a fact that] from time to time something happens in every sport," jockey Josef Vana told the Independent newspaper in 2013.
Held every year on the second Sunday in October, except the during World War I and II, the 1968 Russian invasion and once due to snowy weather conditions, the race takes most jockeys and horses about 10 minutes to finish.
The first Czech winner was not until 1902 -- when Ulrich Rosák was successful.
Several woman have also taken part and won the race since it began, with Lata Brandisova being the first in 1937.
As well as the Taxi Ditch -- which has become a symbol of the race -- other obstacles include the Irish Bank -- an obstacle where horses have to shimmer up and down a steep artificial bank, the French Jump -- where a pair of hedges, spaced closely together, must be jumped as one, and a water jump which is three meters long.
According to Pardubice Race Course, when the race first began in the late participation was low -- with only around five horses and riders involved.
"The horses were mainly foreign-bred, mainly English, German and Hungarian," it says on its website.
"The same is true for the jockeys. In the first decades, English, German and Italian names featured."