Hi arunangelo: Where is the Kingdom of God? When Jesus said in Luke 17:21, "For behold, the kingdom of God is in your midst." To get a clear understanding of what Jesus meant, it is helpful to look at the context of the conversation. In the preceding verse, Jesus was being questioned "by the Pharisees as to 'when' the kingdom of God was coming." (Luke 17:20) Was Jesus actually suggesting that the Kingdom of God was within the hearts of these wicked religious leaders who Jesus had condemned several times? Clearly not! So what was Jesus talking about.
Firstly, remember the account in Matthew 20:21, the mother of the sons of Zebedee came to Jesus asking "Command that in Your kingdom these two sons of mine may sit one on Your right and one on Your left." That is a strange thing to ask if the Kingdom was within someone? In fact, Jesus did promise his 11 faithful apostles that they would be in his Kingdom and "sit on thrones" and "judge" with him in his kingdom. (Luke 22:30)
The reason why she asked this was, secondly, because the Jews believed and were hoping for a literal kingdom government from God will rule over them. Shortly before Passover 33 C.E. when Jesus was entering Jerusalem riding a colt, the crowd welcomed him and some cried out: "to the Son of David! 'Blessed is he who comes in the name of the Lord!'" (Matthew 21:9) Why did they cry this? They had come to recognize that Jesus was the promised Messiah and that "the Lord God will give Him the throne of His father David; 33 and He will reign over the house of Jacob forever, and His kingdom will have no end." (Luke 1:32, 33; Zechariah 9:9) They longed for the salvation, peace, and justice that the Kingdom would bring.
Thirdly, at Jesus' execution, a criminal impaled alongside him pleaded: "Jesus, remember me when You come in Your kingdom!" And He said to him, "Truly I say to you, today you shall be with Me in Paradise." (Luke 23:42, 43) That robber evidently believed that after being raised from the dead, Jesus would enter into a Kingdom in heaven where he would sit at the right hand of his father. (Acts 2:34)
Finally, this kingdom is clearly referred to in the old testament as a literal ruling kingdom. Daniel 2:44, states: "In the days of those kings the God of heaven will set up a kingdom which will never be destroyed, and that kingdom will not be left for another people; it will crush and put an end to all these kingdoms, but it will itself endure forever." Then Isaiah 9:6, 7, says: "For a child will be born to us, a son will be given to us; and the government will rest on His shoulders; and His name will be called Wonderful Counselor, Mighty God, Eternal Father, Prince of Peace. There will be no end to the increase of His government or of peace, on the throne of David and over his kingdom, to establish it and to uphold it with justice and righteousness from then on and forevermore. The zeal of the LORD of hosts will accomplish this."
So, considering what the bible teaches, the kingdom is a real government that Jesus will be the king of, and it will rule over the earth during his millennial rule. (Revelation 20:7, 8)