Body and soul
The most spread idea about the human being was the idea that the soul of the person lives for the certain time in the body of the certain person. And when the body dies and is damaged in some way, the soul goes away to the other world. The travelling to the other world was considered to be long and rather difficult.
The far other world was divided from the real world with the help of steams, mountains, islands and was situated on the island, under the ground, in the sky, etc. And the dead person needed the horses, boats, good shoes, food to eat during his/her travelling. And all these things were usually put into the grave. The person met different supernatural difficulties on his/her way. In such way the person could meet the fire lakes, the boiling steams and canyons. And people had to cross the canyon with the help of the thin bridge. If the person fell from the bridge, he/she died for the second time finally.
There were also companions who helped people to come through all difficulties. These companions could be the animals that are usually dogs or horses, shamans and gods.
The entrance to the other world that is sometimes bridge was usually guarded by some creatures. They were usually huge dogs in the nations of Indo-European group or by masters of the other world. And only those who were buried with all ceremonies and according to all rules were allowed to enter it. But those who haven't made some rite died for the second time or turned in the eternal wonderer.