The Valley of Seven Deaths

Earlier this month I had read a story about a place in India called "The Valley of Seven Deaths".
I read about it in a German book called "Bizarre Wirklichkeiten" by Hatwig Hausdorf. To claim what the author did, This place is being kept secret by the Gorvernment of New-Delhi. Why exactly, I can not tell you, but I would assume that in the case of this story being true, it because numerous expeditions to this place went very very wrong. According to the author, one of the first documented expeditions to there was lead by a man named Graham Dickford around 1890. He had heard stories of numerous tempels with piles of gold in them, which were in this valley. He claimed to had found this valley when he was brought to a not specified hospital somewhere in india in 1892. He was in very bad shape when he arrived there. He had high fever, no more hair on his head which was covered with wounds and bruises, was burnt from head to toe, and was in a state of mind that doctors would call insanity. When he arrived in the hospital he claimed to be the only survivor of his expedition. Alle that man said was: " Big, flying Fire; Shadows in the night; and ghosts, who's glare could kill." He died 3 days after he was brought to the hospital. Noone he was in contact with for his last three days believed a word he said (no wonder), until 1906 when the british government payed for an expedition to this Valley. The only information my research has brought is that this expedition was made of 4 people and two of them stated that, they had found tunnel into caves,looking something similar to a funnel. Two men were sent downthere, and immediatly as they reached the bottom, they are said to have made bizzare, snake-like movements for about a minute, and just fell to the ground. One of the last two people alive goes down the "funnel" about to find out that they were dead. After that experiance they are said to have left the same day and they never came back. These two survivors told relatives that they were bugged by constant headaches and night for night they would have gruesome Nightmares, until eventually they both died about 3 months later.
1911 another expedition to the valley was started. a month after it had started, only two of the original 7 men returned and told people a very crazy story...
They said that they were all building up their tents for the night, when suddently 5 of them started shaking and turning around and around, and after about a minute of this behavior they just fell down dead.
The last documented Expedition was in 1919. 7 very experianced hunters went on the expedition, and the said that there were 17 human corpses looking right at them once they had reached the valley. They also claimed that two of them were standing at a cliff having a conversation, and suddently they were gone without a sound. the others went to look for them, and found out that they had just mysterically fallen down that cliff. Since that time Noone has been there. I don't know what to think of this story though...
I think that if this were real, we would of already known about it don't you think?