According to the Times of Malta, Unesco is thinking of adding the last 2 surviving examples of 100 ton Armstrong guns to their list of World Heritage Sites.  The executive director of the Malta Heritage Trust, Mario Farrugia, mentioned the fact while addressing a tour of Malta's historic Fort Rinella, home of one of the guns.  Originally two guns were installed in Malta and two in Gibraltar in the late 1870's.  The Rinella gun was last fired in 1905 with a full load.  Even Jules Verne was a fan, he remarked on a visit in 1878 that the fort was a marvel of the industrial age, and would render Malta safe forever.  Well, it has been pretty safe since then, but it did get temporarily beaten up in WW2,  but not defeated!

100 ton gun at Fort Rinella