Cac Co cave is in Thay pagoda complex of Sai Son commune (Quoc Oai district, Hanoi) which is concerned for being said to have 3600 skeletons. Crossing the stone steps to come to the top of the pagoda and passing a gliding stone flap, we came to the entrance. The cave is deep and dark; we need to use the torch and stepping carefully to reach the floor. Crossing the vertical staircases, we could see the tank of skeletons. It was a big tank made from stone. There is an altar in front of it and there was a small square enough for the head of the human. Looking in the tank by the torch, we could see many parts of human bones, and a feeling of shivering came. There are some real money, paper money for dead people, etc.
Mr Ta Van Chinh, the guarder of Cac Co cave, told us sensational stories of the skeletons. That was the battle of the general Lu Gia. When he was discovered by the enemy, he lead the soldiers to hide in this cave and when being discovered by the enemy, they used stone to block the entrance and all the people inside were dead.
According to the stories of many generations, Mr. Chinh said they found this cave with the skeletons overlapping each other and they made a tank of stone to put them in. Nobody could list the number of the skeletons but there are statistics written in books of history that there are about thousands of them.
There is also a spring called bone spring in the cave. Mr. Chinh said that was just an exaggeration of people and that was just some bones found in this spring. In order to come to this spring, people have to cross a long path for more than half a day.