St. Johns Co-Cathedral (Kon-Katidral ta’ San Ġwann) is located in Valletta. It was one of the most impressive buildings that I have seen during my visit, and therefore I heartily recommend this one whenever you are in town. It is a Baroque cathedral, and is considered to be one of the world's greatest cathedrals.
See, I didn't expect the interior, given its exterior. The facade is very stark and plain, made with just the limestone that is prominent in the country. One would never expect to see such grandiose ornateness inside, given what the outside looks like. But yes, I went inside, and I was surprised with what I saw.
There were plenty of golden and other glittering material inside. Every panel is pretty much a work of art. There are tombstones on the floor, complete with marble tablets describing who was buried underneath. And yes, there is also Caravaggio's painting depicting the beheading of John the Baptist.
I won't say much about the cathedral, as I will let my pictures speak for itself. It is such a wonderful experience being inside, it's a visual feast that leaves the senses quite mesmerized and out of breath.
So yes, I was wowed by this place. I definitely recommend you to visit this place too, in case you find yourself in Valletta, as I am pretty sure you will be amazed as well.