BioShock Infinite Memorial Gardens, or Chapter 30, is available after DeWitt and Elizabeth reach the gardens, and when they discover that the entrance to Comstock House (the one they find in Downtown Emporia) is locked.
If Booker DeWitt wants to gain access to Comstocks house, he must first open three Tears in order to find out what really happened with Lady Comstock and the Luteces.
The majority of the chapter takes place in the same areas as the previous chapter, but with some important additions.
Therefore, the following collectibles guide details the location of each BioShock Infinite collectible.
When you enter the gardens you need to open the crypt to get Lady Comstocks fingerprint. Things dont go as expected, because Comstock uses Elizabeth to transform Lady Comstock into a ghost.
Battle the ghost and then follow her footsteps (as instructed by the Luteces) to reach the building named Lutece Laboratory (Market District).
Head inside the lab and go upstairs in the bedroom to find an Infusion bottle. Turn around after you pick up the bottle to see the first BioShock Infinite Memorial Gardens Voxophone hidden behind the bed.
A THEORY ON OUR DEATH; Rosalind Lutece; November the 1st, 1909
Head downstairs and open the first Tear. When the Tear closes, pick up the second BioShock Infinite Memorial Gardens Voxophone from the ground (same location as the Tear).
CHILD OF SCIENCE; Rosalind Lutece; January the 4th, 1895
Before leaving the lab, check the room on your right (while facing the Tear) to find the third BioShock Infinite Memorial Gardens Voxophone on a small metallic table.
ON THE ENTROPY OF GENES; Rosalind Lutece; July the 3rd, 1893
Follow the footprints to the second Tear which is inside the bank from the previous chapter (Bank of the Prophet). Use the elevator to reach the banks main hall and get rid of the enemies.
In front of the large vault door, the waypoint tells you to go right, to reach the vaults. Instead of doing that, head left until you find a room filled with safety deposit boxes.
The writing on the wall, HOARDER, is actually the code that needs to be decrypted using the code book you found inside the Hudsons store, in the previous chapter. Assuming you have the code book, use the typewriter to unlock a secret area, then grab the Infusion and the fourth BioShock Infinite Voxophone in Memorial Gardens.
THE IMAGINATION OF GOD; Lady Comstock; January the 4th, 1895
Go back in the main hall and follow the waypoint until you find the second Tear. As soon as you see it, head inside the room to the left.
At the far end of the room is a locked safe. Check behind the safe for the fifth BioShock Infinite Memorial Gardens Voxophone.
NO LONGER; Lady Comstock; January the 5th, 1895
Open the second Tear and then grab the sixth BioShock Infinite Memorial Gardens Voxophone that appears at the base of the statues.
A BROKEN CIRCLE; Zachary Hale Comstock; September the 10th, 1893
Leave the bank, but not before fighting the ghost again. Make use of your waypoint to find the right way to the third Tear, inside the photography store.
Open the Tear and when it closes pick up the seventh BioShock Infinite Memorial Gardens Voxophone from the table.
THE CUSTOMER IS LATE; Rupert Cunningham; November the 6th, 1909
Follow the way back to Comstock Gate and start the final battle against Lady Comstocks ghost. When the fight is over, use the doors to reach the Comstock House.