I have found this little formation of ca. 5 cm (2 inches) near my bedroom window. I have seen no insects crawling or flying around it. I'm in southern Europe (Italy / coastal Tuscany), and it is late Spring.
Is this an insect nest? Maybe wasps? Is it something that I should be wary of, or can I just try and knock it down by myself (with some precautions, by night and after spraying it down abundantly)?