While I was in the Central Business District of Sydney, I also explored a nearby church, which turned out to be the St. Mary's Cathedral. I later learned that it was the largest church in Australia.
I walked in, and thankfully there was no mass being observed. So I was able to check out the interior. Officially, it is called the Cathedral Church and Minor Basilica of the Immaculate Mother of God, Help of Christians, Patroness of Australia. It is in Gothic Revival style, after all, it looks like a 13th century Gothic church, yet it was actually constructed between 1868 and 1928.
I explored the exterior as well as the interior of this church, including the crypt. It was a large building, and it had interesting nooks and crannies that I had to take a peek inside.
Eventually, I slowly made my way out, and headed elsewhere.