Depending on the metric, the human brain is the most complex structure in the universe that we currently know of. Which is a depressing fact considering how primitive the average normie is. I wish there was something bigger, something that we can discover and explore. A bird might not understand how much smarter humans are compared to him, but nevertheless, his sensory organs allow him to experience this greater being, if it is physically close to him.
There is no such thing for us, we only have concepts and ideas of greater beings that exist outside or too far away in the universe. You could say they physically exist in our universe in some way because of the stored information in our brains and the things we created and wrote about them.