Local function definitions typically mean your braces are messed up. Indeed, this is the case.

Code:
int Check_Exp()
{
int your_exp = You.GetExp();
enum {level1 = 20, level2 = 60, level3 = 100};
switch (your_exp) // unclosed switch
{
case level1: cout << "Place holder one";
break;
case level2: cout << "Place holder two";
break;
case level3: cout << "Place holder three";
break;
    default:cout << "Default";
// should close it here
return your_exp;
}