The same that Mary sister of Martha received when she knelt for a long time before the Lord. Thus the Lord speaks about her:
There is no more wonderful time besides Holy Communion than Adoration. Read what the saints write on this topic, and you will be greatly astonished.
I think it’s worth mentioning that in Adoration I received a grace that lead to my conversion, which I describe as a “falling in love” with Christ - and many more, only a few of which I am aware of. Even before I knew about Adoration (or the Eucharist), I used to pray in my heart: “if only I could see Him and be there next to Him in the manner of those who lived in those days…”. I did not know, back then, that the Lord did not leave us orphans, and He did say: “* I will see you again and you will rejoice, and no one will take away your joy. In that day you will not need to ask me for anything.*”. No time better fulfills this than Adoration, especially when we pray the kind of prayer that is called contemplative, in which - as s. Therese of Lisieux once wrote - “we do not tell Him anything…we simply love Him”.