Select visible cells
 

This tool selects all visible cells of a selected range or the entire active sheet.
If no range is selected, the entire worksheet becomes the work area.

The advantage of using this useful tool is the fact that we can easily detect hidden cells -although it does not select them, it does leave a trace in the form of a line.
Look at the row numbers in this example. You will see that rows 9-15 are hidden, but a trace can be seen (a non-selected line).