The Customs House building in Alicante and it's Civil War secret

I must have walked past the old Customs House building on Levante Dock in the middle of Alicante hundreds of times. It's a fabulous old structure. What I didn't realise until very recently is that it hides its own Civil War secret. The section at the far end is actually a fake facade, made up to to look like the rest of the architecture but it concealed a Civil War era air raid shelter, presumably for the crucial dock workers. Seems a bit odd in a way that you would conceal a shelter in such a prominent building and I will try and find out the reasoning. I wasn't able to get in but I have heard that the shelter may be opened up to the public in the future. When I took a trip down some works were underway, I'm not sure if they are part of that project but I was able to get some pictures of the solid stone walls inside. Hope to hear more about this interesting piece of Alicante history in the future.