There are a number of instances where the borders of two or three nations touch, but the rare confluence of a total four nations coming together on one spot only exists in Africa where the corners of Zambia, Zimbabwe, Botswana, and Namibia meet.
The African quadripoint sits in the middle of a river that cuts between the countries. It has been theorized that the point is not a true quadripoint but instead a pair of tri-points separated by thin strips of real estate.
At one point the ferry that carried people across the river from Namibia to Botswana became a point of contention, with both countries laying claim to the transport. A small amount of fighting broke out but it was rather subdued for an international incident.
While many maintain that slight changes in the flow of the Zambezi river and the exact geographical borders have eliminated an actual quadripoint, the countries are all so close that the only difference is academic.
According to atlasobscura