Zevachim 59 - Sacrifice Rejection, Damaged Altar
If a sacrifice was slaughtered, and then the Altar became damaged, this sacrifice is rejected. It cannot become valid again, even after the Altar is repaired.
However, Rav commented on the reverse situation, "If the Altar became damaged, all sacrifices that were slaughtered there are disqualified, and there is a verse for that, but we have forgotten it." When Rav Kahana went to Babylon, he heard Rabbi Shimon teaching the verse that states "On the Altar you will slaughter your burnt offerings..." But, he asked, you are not slaughtering them ON the Altar, but at its side, so what does it mean? That your offerings are valid only when the Altar is complete. Said Rav Kahana, "That is the teaching that slipped away from Rav!"
How large was the Outer Altar that Moses built? It was 10 by 10 cubits, and 3 cubits high - according to Rabbi Yehudah, but according to Rabbi Yose it was 5 by 5, with a height of 10. And how large was the Outer Altar in the Temple? It was 30 by 30 cubits, with a height of 10.
Art: Edgar Degas - Semiramis Building Babylon, 1861