The Pharisees were wanting some miracles today so they asked Jesus wohen the kingdom would come. Jesus told them there would be no fireworks or hype or powerful display. Most people don't see the kingdom of God nor can they tell you where it is. The reason is that it's in our hearts and it's a spiritual Person, the Holy Spirit, surrounding us.
In Luke 13:18 Jesus says that the kingdom of God is like a seed tossed outside. It grows into a tree that is a sanctuary for the birds to nest. If the seed of Christ's love is planted and grows in us, we'll be more than knowledgeable, selfish Christians. We'll be a place that people will come for mercy and grace and rest. And there are a lot of people in need of those.
In the kingdom there are secrets. Mysteries of the past, present and future are hidden there. Jesus talked to the crowds in parables but His true disciples He talked to plainly, with the meaning of the parable. One secret (1 Corinthians 15:51) is that we won't all die but we'll be changed. Hope is often given to us and this is hope: to become heavenly rather than going through a usual earthly end.
From Scriptures (Mark 4:11 AMP), (Luke 17:20, 21 AMP)