Gates" in ancient times had a significance that does not hold in the modern world. Cities then were enclosed by walls for protection; gates in the walls let people in and out to do their business, but were also the weak points in the cities' defenses. In the Bible, cities on one level represent the minds of individual people. On a broader level, they represent beliefs shared by a community. The gates, then, represent openings where the Lord can feed us an understanding of truth and a desire for good. They also represent points where the hells can invade and sway us with false ideas and evil desires. We are kept in balance during our lifetimes, with influences from both the Lord and from hell. Ideally, we will over our lifetimes continue to invite the Lord farther and farther in and drive the hells back until ultimately the Lord can occupy our minds completely. And that point our belief in Him and His power and love will hold the gates and deny evil any entrance. As individuals, we at that point become angels. As communities, we at that point become part of the Lord's church. And at that point the gates become an entry point, introductory truths that allow people to enter churches and start bringing the Lord into their lives.

The first altar mentioned in the Word was the one built by Noah after he came out of the ark, after being saved from the great flood. On that altar, he sacrificed clean animals to the Lord.

Mountains represent the Lord because of their height; we need to raise our thoughts above worldly things when "talking" with the Lord. An altar is a small artificial mountain. When it's used in worship, it can call to mind this raising of thought. The fire and smoke that rise from an altar are symbolically being sent to the Lord.

Most altars were made from unhewn stones. Stones represent truths. Unhewn stones - ones that have not been shaped by men - represent truths from the Word, truths that have not been adulterated.

The clean beasts to be sacrificed represent good things, charitable acts done because they are right. The clean birds represent thoughts about doctrine and actions, and about what is right. Presenting these things is an acknowledgment that we have them from the Lord, and a giving thanks to Him for them.

In the Israelitish Tabernacle, the altar of burnt offering represented the acknowledgment of good and the altar of incense that of truth. For this reason this larger altar, which was outside by the door, was made of brass which signifies natural good, while the altar of incense was made of gold, which signifies love to the Lord from whom comes truth.