Anyone who lives downtown in Vancouver has heard this, even though they may not realize it. My first few months in Gastown, I would consistently hear a deep thud at around 9:00pm. I kept assuming that it was trains from a nearby train yard docking, but later found out about this bad boy.

If you're able to see it at low tide, like in this shot, you can get down onto the rocks for a better angle. However, it will likely be very busy with tourists, so you may need to do some compositing, like I did with this shot.

Also, bring earplugs. It's a cannon, after all.

https://en.wikipedia.org/wiki/9_O%27Clock_Gun