Everything that your sense see is an illusion! Just like in your night dream you experience a city which does not actually exist yet appears to be true for the period of the dream, so too the waking world is as illusory as the night dream.
What is Truth?
That you are the witness of a dream is true!
The dream and whatever you saw in it are illusions!
There is only One I! you are that! Many is an illusion!
Solid matter is an illusion projected by thoughts!