In C++, try-catch blocks can be nested within other try-catch blocks. This is useful when dealing with complex functions or algorithms that may throw multiple types of exceptions at different levels of abstraction.

The syntax for nesting try-catch blocks is straightforward. Here's an example:

try {
  // code that might throw an exception
  try {
    // nested code that might throw an exception
  }
  catch (exception_type2 ex2) {
    // handle exception of type exception_type2
  }
}
catch (exception_type1 ex1) {
  // handle exception of type exception_type1
}

In this example, if an exception of type exception_type2 is thrown inside the nested try block, the inner catch block will handle it. If an exception of type exception_type1 is thrown in either the nested try block or the outer try block, the outer catch block will handle it.

It's important to note that the nested try-catch block must be fully contained within the outer try block. If an exception is thrown in the inner try block and there is no catch block to handle it, the exception will propagate to the next level of the stack, which in this case is the outer catch block. If there is no catch block in the outer try block to handle the exception, the program will terminate with an unhandled exception.