<p>In Madrid I saw a huge number of Spanish flags draped over people's balconies and hanging in windows.  It was very striking indeed. 
</p><p>Not knowing the city, I cannot be sure that this isn't normal. However, I suspect it is not. 
</p><p>My guess - though it is only that - is that it is a response to events in Catalonia. The Catalan government declared independence after a referendum that the Spanish government judged to be illegal. 
</p><p>The prospect of Catalonia wanting to break away has perhaps prompted a response from those who wish to reaffirm the unity of the Spanish state. 
</p><p>One display of nationalism generates another: an equal and opposite reaction. 
</p><p>Madrid, as the national capital, may have a disproportionately high number of people of that view. Hence the number of flags on display. 
</p>
Though there are many in Catalonia itself who are opposed to independence too.
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<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/158710843@N02/27990166949/">Spanish flags draped over balconies - Madrid</a>