A marble altar can be built in the Altar space of the Chapel in a player-owned house. It requires 70 Construction to build and when built, it gives 1,030 experience. The player must have a hammer and a saw in their inventory to build it.
It gives 200% Prayer experience when bones are offered at it. With one incense burner lit it gives 250% Prayer experience, while with two lit incense burners it will give 300% experience.
Training Prayer with this altar is inadvisable as the gilded altar requires only a few more Construction levels to build and provides more experience per bone.