Well it depends which altar you're looking for, i know there are a couple by the black night's fortress. Other than that, you have to have the corresponding talisman (air, water, fire, body, etc.), right-click it, and it should have something like, "locate talisman". When you click that, it will tell you which way to go. Plus, you have to have the talisman with you to get in.
The air altar is between Varrock and the Barbarian Village (i.e., west of Varrock). When you go the first time, take an air talisman; it has an option to tell you the in what direction the air altar is. Similarly, you can use the specialized talismans for the other altars. In any case, you need either an air talisman or an air tiara to actually get into the altar.
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The water altar is located at lumbridge swamp south of lumbridge castle it is found near a hut in the area of the swamp
Tiaras are a type of clothing in the game, RuneScape. They can be binded to a runecrafting altar, and you will get a themed tiara of that altar. for example, air tiara. And then it can be used to have one click access to the altar, and you don't need a talisman.
It is in the Lumbridge swamp.
The altar locations are located by a "rune" icon on the world map. You can also find specific altar locations by Googling "Runescape Altar Map".
At the air altar in Varrock.
pray at the astral altar
woodcutiing yews (lvl 60) mage logs (75) fishing 62 (members) monkfish sharks 81 i think... mine god for lvl 70 Adam ore runecraft 50, law runes
Speak to estate agents in Runescape. One of them is in east varrock just opposite the altar
North-East Varrock. The talisman will help you.
Get rune essence and craft them at the air altar.