As Congolese government troops and UN peacekeepers engage in fierce fighting with rebel forces in the east of the Democratic Republic of Congo, BBC World affairs correspondent Mark Doyle assesses why it is such a volatile region.
Eastern DR Congo was once memorably described by the journalist Kate Thomas.
The place "looks like heaven", she wrote, "but it feels like hell".
She was right. There are towering volcanoes, rushing rivers and sparkling lakes. Heaven indeed.
And there are, above all, the hills - the green, rolling and fertile hills that stretch from the current conflict zone, right across the border into neighbouring Rwanda, which is itself called the "Land of a Thousand Hills".
That should be a clue as to why eastern DR Congo is also hell.
The geopolitics of central Africa have tied the heart of eastern DR Congo, the provinces of North and South Kivu, whether they like it or not, to Rwanda.
After the genocide of Rwandan ethnic Tutsis, in 1994, the killers - the Rwandan army and a large proportion of the entire population of ethnic Hutus - were militarily defeated and chased into DR Congo.
Some of them remain in eastern DR Congo as a militia force which, according to Rwanda's now dominant Tutsi rulers, could threaten genocide again.
But in the intervening years another force also emerged in eastern DR Congo, this time a Congolese Tutsi force, led by a self-declared general, who said he was protecting Congolese Tutsis from the Rwandan Hutu militia.
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