It's a wonder former inmate Ntaza Talakumeni can bear to hear the sound of a steel door closing. But he slams it for effect – the vibrations thundering through our bones, we shriek and he laughs. There are four such barriers between a cell and the outside world, but one is enough to understand that life here is brutal.

Robben Island maximum-security prison housed many political detainees in apartheid-era South Africa.

Prisoner 466/64 spent 18 years behind the four steel doors, in B Section, sleeping on the floor on two rush mats, with four thin blankets, a bucket and a small table in cell No.7.

Like his fellow inmates he was badly treated, frequently beaten, had no privacy and was afforded just 30 minutes' exercise a day and one family visit twice a year.

His crime? Opposing the political regime that made him a second-class citizen for the colour of his skin.

The man was Nelson Mandela, leader of the African National Congress, former president of South Africa, its first black president, who died in December .

Perhaps more importantly, he also shared the Nobel prize for peace with the man who paved the way for his release and the end to Apartheid, FW de Klerk, whom he succeeded in 1994.

This year marks the 20th anniversary of democracy in South Africa, and it's a great time to visit.

I pay a visit to follow in the footsteps of Mandiba, to give him his Xhosa clan name, or "the father of the nation" as he has come to be known.

Before setting off, I had been warned umpteen times to be wary of violence and crime. I expected to experience an air of tension but found none, either in Cape Town or Johannesburg.

Instead, I find a warm and friendly welcome from people delighted at the interest foreigners take in their country and their iconic former leader.

Mandela is like a thread that runs through this society, and much of South Africa's tourism industry focuses on him, his ideals and his legacy.

The recordings of the inmates of Robben Island, alongside a few personal possessions in their former cells, make for uncomfortable listening at times. Tales of teenage boys being buried up to their necks in sand, being urinated upon, tortured and sexually abused were unemotionally confirmed by the inmate guides.

"How do you forgive this?" many of the tourists ask. "Africans are happy and forgiving people," Ntaza says. "Mandela learnt forgiveness in this place and he told us to forgive and not to take revenge. Revenge would have solved nothing. It would not have helped South Africa."

Ask anyone what it meant for them and they are only too happy to share their experiences. My city guide Gledwin was detained without trial for six weeks as a schoolboy in 1983, during the state of emergency. A month of this was spent in solitary confinement and he was beaten and tortured.

He takes me to District Six, an area close to the centre of Cape Town that once housed a bustling township community. In 1966, it was declared a whites-only district and in the next few years, the 60,000 residents were forcibly removed 25km to the bleak Cape Flats township near the airport.

This is not warm, fuzzy tourism. You can do the beaches and safaris and ignore the history, but what a wasted opportunity.

You can even do a Mandela food tour. At the Gugu Lethu township Sheila Tempi serves a sumptuous spread of Mandela's favourite foods, while her husband, Blackie, serenades us with jazz on his trumpet. I'd consider myself a fair linguist but the Xhosi clicks are far more difficult to get my mouth around than the izibindi zenk (chicken livers) and isonka sanzi (steamed bread).

Cape Town has undoubtedly experienced more than its fair share of trouble, yet it is understandably proud of its heritage, and now it is blazing an exciting trail.

Woodstock, a previously run-down and neglected area in the centre of the city, has been reborn as the go-to place for young designers. It houses the Woodstock Exchange and The Old Biscuit Mill, with boutiques, studios and galleries, cafes and artisan businesses and restaurants.

The Neighbourhood Goods Market takes place every Saturday and is a thriving melting pot offering fashion and crafts, and a vast array of fresh produce. Another one has sprung up in Johannesburg in what looks like a multi-storey car park.

No wonder, then, that Cape Town is the World Design Capital 2014. Everything here is noise and colour and it's easy to see why South Africa is called the Rainbow Nation.

Where Cape Town has Woodstock, Jo'burg has Maboneng Precinct. This is another former run-down inner-city district that has become the gentrified centre of all things contemporary and innovative.

The 12 Decades boutique hotel, complete with finger-print entry points, is on the rooftop of the Main Street Life Building. The 12 rooms are designed and conceptualised by some of the city's most celebrated artists and designers, to chronicle a particular decade in the city's history. I particularly like the toilet pan decorated with the apartheid laws.

Soweto is a place that, for those who remember the apartheid era, will be synonymous with poverty, uprisings and violence.

A cycle tour soon reveals a different side of the South West Township. Mandela's house is far less interesting than the bustling churches, with their stunning singing and dancing congregations. Music emanates from every home and every child wants a "high-five" or a photo from the cycling tourists.

Tickets to the Apartheid Museum highlight segregation with randomly issued whites only and non-whites tickets that mean we have to enter the building via separate entrances.

South Africa is the first African country and second in the world after the UK to develop a National Minimum Standard for Responsible Tourism. This focuses on sustainable tourism, which means among other things, authentic experiences.

* Liz Fullick was a guest of South Africa Tourism (southafrica.net). She stayed at the Taj Hotel Cape Town (tajhotels.com) and 54 On Bath in Johannesburg (tsogosunhotels.com).