There are many reasons why Nanjing is popular with weekend travelers. Part of the attraction is the splendid natural setting. Straddling the south bank of the Yangtze some 185 miles west of Shanghai, the city is sheltered by hills to the south and east, and its urban landscape is beautified by parks and lakes. The city's hearty local cuisine, particularly its much-cherished duck and fish dishes, adds extra allure. And easy access enhanced by frequent high-speed trains that take around two and a quarter hours is further positive attribute.

But it is Nanjing's history that really magnetizes visitors. China's 'southern capital' has been the nation's principal city on three occasions - during medieval times, again in the early years of the Ming dynasty, and for a third time during the Republican era leading up to World War II. Consequently, it is rich not just in historical sites, but also in the intrigue that surrounds them. Short-stay visitors often head first for the handsome remains of the zig-zagging 26-mile-long ancient city walls, and then the mazy courtyards of the former Presidential Palace. The itinerary might then decamp to the shaded slopes, Ming Tombs and Sacred Way, a stately guard of 12 pairs of life-size stone animals including lions, elephants and camels, of Zijin Shan. A natural climax is the lung-busting climb up the steep stone stairway to Sun Yatsen's Mausoleum.

History, and the people who make it, are never uniformly kind to any city, however. And, as several filmmakers have attempted to capture in the past year, twentieth-century Nanjing dissolved into periods of deep darkness. As the inevitability of World War II seeped across the continents, Nanjing experienced suffering of the kind that those of us who have never witnessed systematic bloodletting cannot expect to comprehend. In December 1937, the Japanese occupation turned murderous. A six-week killing spree left scores of thousands dead. The legacy of what happened here hangs indelibly over Nanjing, and has shaped the city's responses to the challenges it faced in the intervening seven decades.

While researching her book The Rape of Nanking, author Iris Chang repeatedly encountered a hitherto largely unfamiliar name. Having subsequently contacted a living relative, Chang discovered the diaries of John Rabe - and the story emerged of the 'Good German of Nanjing.' Renovated and reopened in 2006, Rabe's three-floor cottage - which became a sanctuary to around 600 Chinese fleeing from the killings - stands beside the entrance to Nanjing University (Nanda) on Guangzhou Lu. But blink and you will miss it.

Founded and funded at the turn of the twentieth century by American missionaries, Nanda's tree-lined boulevards, time-worn red-brick classrooms and sculpted lawns meander across the gently irregular topography north of the city center. The pick-up basketball games on dusty courts are technical and competitive, and the conversations in shaded gardens are both intimate and earnest. The dormitories have long since shown their age and the newer buildings lack the same architectural gravitas, but the whole is plentifully superior to its individual parts.

The story of Rabe has been liberally told in both written and movie form, but that does not lessen the emotional impact of visiting the house. A long-time employee of Siemens in China and a Nazi party member, Rabe became Chairman of the International Committee of the Nanjing Safety Zone. His interventions saved hundreds of lives, and, crucially, offered hope to countless more seeking to escape with their life. Entering the compact walled courtyard, with a bust of Rabe in the centre and the sealed entrance to an underground shelter at the back, is an emotive experience. Desperate human beings once herded together here to avoid brutal death.

Rabe's House serves as a scene-setter for the more architecturally powerful Memorial Hall to the Victims of the Nanjing Massacre. Located near the old wall's Jiangdong Gate in the southwest of Nanjing, the memorial was first built in 1985, and enlarged in 1995. In 2007, to mark the 70th anniversary of the massacre, it reopened after two years of renovations. The resulting structure, with its high slate-grey panels, sharp-angled black walls, elongated peace lake, memorial friezes and plinthed statues shares may physical elements with other holocaust remembrance centers around the world. Some of its exhibitions though are, by any comparative standards, graphic and emotive.

Viewed from above, the memorial is shaped like an obelisk, with a sharpened pyramidal point running parallel to the entrance walkway. Here, a series of sculptures depict scenes of man-made tragedy. The most haunting is a soaring copper figure of a young mother, her head tossed back in grief and a lifeless baby held in her arms. Strategically spaced, these statues flank a thin moat separating visitors from the layered concrete and glass building. The effect is disturbing. It's impossible not to glimpse your own reflection behind the sculptures - which asks awkward questions of our personal responses.

The memorial entrance is a split bronze rock, featuring the hand of a fallen body reaching skyward. Inside, the large pebbled compound is noticeable for its sense of space - and solemn emptiness. At the back, stands a large cross, dated 1937.12.13 - 1938.1, signifying the time span of the events commemorated. Behind. emblazoned across a large black wall, are the words '300000 Victims' written in 11 languages.

The two most poignant sections follow in close proximity. The first is a 43-meter Crying Wall inscribed with the names of those who perished. The impact of the second section is more chilling. Nothing stirs untapped human emotions, nor questions our own sense of existence, like the sight of a human skeleton. Inside an open tomb, covered overhead from the elements, lay 227 bodily remains. Treated with state-of-the-art preservation technology, the bones lay twisted and partially embedded in the layered earth. A simple numbered plaque sits beside each carefully spotlit human remain. The numbered skeletons are a visually uneasy reminder of both the pointlessness of warfare, and of the absolute necessity not to betray the victims of past cruelties by creating new tragedies.

And that, if nothing else, is a compelling reason for visiting Nanjing.