The Grand National is run at Aintree, Merseyside. Aintree is a left sided course with 16 fences including the infamous Becher's Brook, Foinavon's, the Canal Turn, Valentines Brook and the Chair among others. The Grand National covers two laps of the track, which means a gruelling 4 ½ miles (3 ½ furlongs) and 30 fences to overcome just to finish, let alone win the race.
It is generally considered to be the most difficult course to complete, a view that is backed by the stats. In 1928 only 2 horses completed the grand national and as recently 1988, only 9 horses finished. Over recent years, due in particular to changes made to the course for safety reasons (see below), a greater number of horses complete the race. The average number of finishers over the last 6 years is 17.
You can take an overview of the course here: Aintree Horse-eye view
Arguably the most famous of the fences at Aintree is Becher's Brook, named after the spot where Captain Becher lost the lead in the first "official" Grand National in 1839. At the time the fence was known as the First Brook. Becher lost his mount and fell, diving for cover into the brook itself as the other horses cleared the obstacle. Legend has it that he was heard to tell the spectators that he did not realise how filthy water tasted without the benefit of whisky! Until 1991, Bechers brook consisted of a 4-foot-10-inch barrier, with a brook on the other side rising from a depth of 5 feet, 6 inches. The lower landing took many by surprise and caused several injuries and deaths to horses. From 1991, the Brook was filled in, softening the impact of the landing. The course features several well-known fences such as "the chair", "Foinavon" and "Valentines Brook"