Youcat commented through CCC – Question n. 518 – Part I.

YOUCAT Question n. 518 - Part I. If the Father is “in heaven”, where is that heaven?

(Youcat answer) Heaven is wherever God is. The word “heaven” does not designate a place but, rather, indicates God’s presence, which is not bound by space and time.

A deepening through CCC

(CCC 2794) This biblical expression does not mean a place (“space"), but a way of being; it does not mean that God is distant, but majestic. Our Father is not "elsewhere": he transcends everything we can conceive of his holiness. It is precisely because he is thrice holy that he is so close to the humble and contrite heart. "Our Father who art in heaven" is rightly understood to mean that God is in the hearts of the just, as in his holy temple. At the same time, it means that those who pray should desire the one they invoke to dwell in them (St. Augustine, De serm. Dom. in monte 2, 5, 18: PL 34, 1277). "Heaven" could also be those who bear the image of the heavenly world, and in whom God dwells and tarries (St. Cyril of Jerusalem, Catech. myst. 5:11: PG 33, 1117).

Reflecting and meditating 

(Youcat comment) We should not look for heaven above the clouds. Wherever we turn to God in his glory and to our neighbor in his need; wherever we experience the joys of love; whenever we convert and allow ourselves to be reconciled with God, heaven opens there. “Not that God is where heaven is, but rather heaven is where God is” (Gerhard Ebeling). 

(CCC Comment)

(CCC 2796) When the Church prays "our Father who art in heaven," she is professing that we are the People of God, already seated "with him in the heavenly places in Christ Jesus" and "hidden with Christ in God" (Eph 2:6; Col 3:3); yet at the same time, "here indeed we groan, and long to put on our heavenly dwelling" (2 Cor 5:2; cf. Phil 3:20; Heb 13:14). [Christians] are in the flesh, but do not live according to the flesh. They spend their lives on earth, but are citizens of heaven (Ad Diognetum 5: PG 2, 1173).

 
(This question If the Father is “in heaven”, where is that heaven? is continued)