Tomorrow

Tomorrow is the name given by Guy to a place he believes is paradise and can only be reached by riding the sun. He and Belt started searching for Tomorrow soon after his family died.

Lore
Upon meeting the Croods, he also told them about Tomorrow which interested them all except Grug and told them that to get there they would need to reach the highest mountain in the distance.

Near the end of the film, they manage to reach the other side of the mountain and are close to the sunset, however the terrifying earthquakes catch up to them and leave them trapped and the smoke from the magma below clouds the sun, making them lose hope. Luckily they soon notice that the light of the sun is still beyond the smoking chasm, so Grug throws his entire family over it and they all safely land on the other side. Eventually Grug, along with several other creatures manages to cross over and upon exploring the new land they find a beautiful seaside paradise. All of them then cheer with joy as they have finally found their Tomorrow