What works projects could the Romans have achieved with black powder?

If they discovered black powder, aside from any weapons application I'm sure they'd realize how valuable it would be for engineering projects. What are some things they could have developed that they were unable to without?
 
The Corinth Canal would be near the top of the list often proposed by Roman Emperors, even started under Nero but not completed until the mid 1800's our time.
220px-Isthmus_of_Corinth.svg.png
 
Mining operations and quarrying spring to mind! The reduction in wood use should probs to be advantageous long term in reducing deforestation in later imperial period (only way to deep mine or quarry was to use wood setting/fire up until invention/perfection of gunpowder) by itself!!!!
Canals of all types, one mega project other than Corinth canal would be the connection by water of the Danube and the Rhine river systems.
Siege operations will naturally flow from the perfection of gunpowder mining methods so sapping is in big styleee!
 
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