Christians -- at least -- should NEVER talk about God being a liar. And since you had to bring this up, God now makes you a liar through Scripture.
Well let's take a look at that, shall we?
GOD made a blood covenant with Abraham as surety that he would receive the land that GOD promised him. Again, GOD would be a liar if he didn't give the land to Abraham.
And [GOD] said unto him, I [am] the LORD that brought thee out of Ur of the Chaldees, to give thee this land to inherit it. And [Abram] said, Lord GOD, whereby shall I know that I shall inherit it? ... In the same day the LORD made a [blood] covenant with Abram, saying, Unto thy seed have I given this land, from the river of Egypt unto the great river, the river Euphrates: Genesis 15:7-8, 18
The book of Hebrews says that Abraham looked for a city built by GOD.
By faith [Abraham] sojourned in the land of promise, as [in] a strange country, dwelling in tabernacles with Isaac and Jacob, the heirs with him of the same promise: For he looked for a city which hath foundations, whose builder and maker [is] God. Hebrews 11:9-10
John saw the city built by GOD descending from heaven to where men are. Obviously it was not with men before it descended.
And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband. And I heard a great voice out of heaven saying, Behold, the tabernacle of God [is] with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, [and be] their God. Revelation 21:2-3
Therefore, the only logical conclusion is that the new Jerusalem descends from heaven to earth where Abraham is enjoying his inheritance that GOD promised him. GOD is not a liar.