Mountain
The Lord's love is the sun of heaven, and it is natural for us to look above ourselves to the sun of this world in thinking about the Lord. It follows, then, that to be closer to the Lord we would climb into the highest places -- and indeed, people have been worshiping on mountains for ages. In fact, even steeples on modern churches are symbolic mountains. It makes sense, then, that a mountain in the Bible represents love to the Lord, the highest, purest love we human beings can experience. Mountains can also represent the desire for good that comes from the love of the Lord. Hills, meanwhile, represent a love of other people and a caring for them, and when "mountains" is used in the plural it generally represents both loves.
Luke 18:15-17
15
They were also bringing their babies to him, that he might touch them. But when the disciples saw it, they rebuked them.
16
Jesus summoned them, saying, "Allow the little children to come to me, and don't hinder them, for the Kingdom of God belongs to such as these.
17
Most certainly, I tell you, whoever doesn't receive the Kingdom of God like a little child, he will in no way enter into it."
