On the day of the inauguration, I was overwhelmed with a sense of history. In the first decade of the twentieth century, a few years after the bitter Anglo-Boer war and before my own birth, the white-skinned peoples of South Africa patched up their differences and erected a system of racial domination against the dark-skinned peoples of their own land. The structure they created formed the basis of one of the harshest, most inhumane, societies the world has ever known. Now, in the last decade of the twentieth century, and my own eighth decade as a man, that system had been overturned forever and replaced by one that recognised the rights and freedoms of all peoples, regardless of the colour of their skin.

Explanation:

 

Mandela was overcome with a sense of history on the day of the inauguration. The white-skinned peoples of South Africa patched up their differences and established a system of racial control against the dark-skinned peoples of their own land in the first decade of the twentieth century, a few years after the brutal Anglo-Boer war and before his birth. The edifice they built became the foundation for one of the world's darkest, most cruel societies. That system had been overthrown forever in the last decade of the twentieth century, and in my his own eighth decade as a man, by one that recognised the rights and liberties of all peoples, regardless of skin colour.

 

Meanings of difficult words:
 
Sl. No
Words
Meanings
1
ValleyA low area of land between hills or mountains, typically with a river or stream flowing through it
2
CrestThe top of a mountain or hill
3
RipeHaving arrived at the fitting stage or time for a particular action or purpose
4
DownpourA heavy fall of rain
5
ShowerA brief and usually light fall of rain, hail, sleet, or snow
6
IntimatelyIn a way that involves detailed knowledge
Reference:

National Council of Educational Research and Training (2007). First Flight. Nelson Mandela: A Long Walk to Freedom - Nelson Rolihlahla Mandela (pp. 16 - 23). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi..