The approximate location of Ryuchi Cave is in the northern part of the Land of Fire, bordering the Land of Rice Fields.
Why "approximate"? Because when Orochimaru was teleported out by the White Snake Sage, Ryuchi Cave was already entirely out of sight.
It is truly not easy for an ordinary person to find. Not only is there a barrier blocking the outside, but the surrounding maze of illusions alone is not something an average person can push through.
Chapter 52