Towards the northern border of the city, the density of development decreases, leaving large areas of undeveloped land around Midrand.[#endnote_] Grand Central Airport is also located in the area. The first suburb to the north of the inner city is Parktown, which is located on a hill overlooking the inner city and Hillbrow. It has many wealthy residents and Edwardian-style mansions, as well as the Education and Medical campuses of the University of the Witwatersrand. The large concrete Charlotte Maxeke Johannesburg Academic Hospital dominates the skyline of Parktown. There are numerous office parks in the suburb as well. Just to the west of Parktown is Westcliff and Parkwood, which is one of the wealthiest areas in Johannesburg, as it is located on the side of a very tall hill and overlooks the inner city as well as the northern suburbs. Other wealthy residential suburbs, Saxonwold, Houghton and Oaklands continue to the north of Westcliff. Nelson Mandela had a house in Houghton, and it is also the location of the most prestigious secondary schools in Johannesburg. Houghton is also the former electoral district of Helen Suzman, a famous anti-apartheid Member of Parliament.