The boots are located at the Mendel Family Library. It's to the west of the entrance to the Failsafe facility, on the second floor of the area.
A solitary Houdini Splicer guards the Big Daddy Boots and Damage Research 2 Combat Tonic. Incendiary Bolts, Liquid Nitrogen and Pistol Rounds are available.
When you complete your Big Daddy's outfit, return to the Main Hall and take the stairs down to the first floor. As Tenenbaum instructs, find a vent along the wall and hit the base of it with the Wrench. The Little Sister will come out to unlock the door for you. Proceed through the Bulkhead to the next level, Proving Grounds.
Check out this BioShock Walkthrough - Point Prometheus shared by Visualwalkthroughs.com.
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