Nirvana bears no resemblance to anything in your current perceptual field.
All of the universes are but phantoms, mirages, and while they have their own essence, their own pantomime - they pass forgotten.
There is a spirit that guides us, if we will listen. It speaks softly. In order to hear it we must still our thoughts and meditate.
When you're around the aura of humanity in those cities, you can't feel anything.
Without innocence, nothing can further, as they say in the I Ching.
Mysticism is the hidden way. It is the most difficult to discuss, because it involves the exploration of perceptual states which are difficult to describe in words.