We learn that God loves us unconditionally. But then why is there Hell? That doesn’t seem unconditional.

Perhaps you would agree that if someone loves someone else, that love would not include him forcing his will on the other. And while it is certainly true that the Lord wills to save everyone, he does not force us to accept his. God is not a slave driver, he is Love and love invites us to freely accept his offer of an eternal relationship. 
 
While some think that everyone wants to go to heaven, generally they have a heaven in mind of their own design. But the real heaven is not merely a human paradise; it is the Kingdom of God and all its fullness. In heaven is celebrated: Charity, worship of God, truth, chastity, forgiveness, esteem of the poor, humility etc. And yet there are many who reject some or all of these values. Why would a loving God force people to enter into the eternal place which celebrates things they reject? 
 
Hence, the existence of Hell is not opposed to God's love. It is in conformity with the respect necessary for our freedom to accept or reject the relationship of love. Mysteriously, many come to a place in their life where they definitively reject God, and the values of the Kingdom he offers.