The Comrades Marathon is an ultramarathon

Ultramarathon

An ultramarathon is any sporting event involving running longer than the traditional marathon length of .There are two types of ultramarathon events: those that cover a specified distance, and events that take place during specified time...

 of approximately 90 km (approx. 56 miles) run in the Kwazulu-Natal Province of South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

 between the cities of Durban and Pietermaritzburg. It is the world's largest and oldest ultramarathon race. The direction of the race alternates each year between the "up" run (87km) starting from Durban

Durban

Durban is the largest city in the South African province of KwaZulu-Natal and the third largest city in South Africa. It forms part of the eThekwini metropolitan municipality. Durban is famous for being the busiest port in South Africa. It is also seen as one of the major centres of tourism...

 and the "down" run (89km) starting from Pietermaritzburg

Pietermaritzburg

Pietermaritzburg is the capital and second largest city in the province of KwaZulu-Natal, South Africa. It was founded in 1838, and is currently governed by the Msunduzi Local Municipality. Its "purist" Zulu name is umGungundlovu, and this is the name used for the district municipality...

.
The race is run on the roads of KwaZulu-Natal Province, marked by "The Big Five" set of hills.