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.

2121. The Last Judgement is now imminent, but this is not so clear on earth and within the Church as it is in the next life, to which place all souls go and flock together. At the present time the world of spirits is full of evil genii and evil spirits drawn for the most part from the Christian world. Among them nothing but forms of hatred, revenge, cruelty, disgusting behaviour, and also scheming devices prevail. This is the situation not only in the world of spirits where souls recently arrived from the world first gather, but also in the interior sphere of that world where those people are who, as regards their intentions and ends in view, have been interiorly evil. This interior sphere is at the present time so full to capacity that I have wondered that so vast a number could ever exist. For all are not cast down into the hells instantly, since the laws of order ensure that every such person shall return to the life that was his during his lifetime, and from that point be taken down step by step into hell. The Lord casts no one down into hell, but everyone does so to himself. Consequently those worlds of spirits are completely full to overflowing - with the vast number of such souls gathering and remaining there for a time. Because of them souls coming from the world are horribly oppressed. And in addition the spirits who are present with a person - for everyone is governed by the Lord by means of spirits and angels - are stirred more than ever before to afflict him with wicked suggestions, doing so to such an extent that the angels present with him can scarcely ward them off, but are compelled to flow into that person from further away. From this situation as it exists in the next life it is quite clear that the final period is imminent.