I automatically think of hill climb racing courses:
The Knox Mountain Hillclimb
http://www.knoxmtnhillclimb.ca, is run annually on Knox Mountain Park Road, in the City of Kelowna. The road, while paved, is narrow with off-camber corners, and steep grades; a nice Sunday drive, but hardly a race track. It is 2.2 miles (3.5 km) long, and climbs approximately 800 feet (245 m) in elevation for an average grade of 6.7%.
Pikes Peak International Hillclimb held at Pikes Peak, Colorado. The 12.4 mile course finishes at a height of 14,100 feet.
"Race to the Sky" is based near Queenstown. Starts from the floor of the Cardrona Valley and runs uphill for 15 kilometres through 137 corners to the top, climbing from 1,500 ft to 5,000 ft averaging a 1:11 gradient.
I could imagine some thigh burn on these courses.