Though you pass through the Zanarkand Temple as part of the main plot in "Final Fantasy X," you do not go to the destruction sphere during your first visit. Once you made your way through the temple and defeated Yunalesca, you return to Zanarkand with the airship and obtain the destruction sphere. The two puzzle rooms in Zanarkand Temple hold the key to the destruction sphere's location. By stepping on specific floor spaces in each room, you'll reveal its hiding place.
Return to the Zanarkand Temple and proceed north to the first puzzle room. Here, you must locate and step on the three spaces that form white squares when lit. The first space is in the far left column, fourth row from the bottom. The second space is in the fourth column from the left, in the sixth row up. The third space is in the second column from the right, second row from the top. After you light all three squares, head through the north door to the second puzzle room.
Enter the second puzzle room. Here, there are four spaces that will form white squares when lit. The first space is in the seventh column from the left, fifth row from the top. The second space is in the second column from the right, fourth row from the top. The third space is in the fourth column from the left, ninth row from the bottom. The fourth space is in the second column from the right, ninth row from the bottom. Once all seven white squares are lit, a hidden door opens in the first puzzle room to reveal the destruction sphere.
Return to the first puzzle room and grab the destruction sphere from the pedestal behind the newly opened door. You can now take the sphere back to the second puzzle room. Place it to the right of the screen and a treasure chest will appear. Open it to claim Yuna's Magistral Rod as your reward.