From the top of Fort Pickens' west bastion, you can see a band of white sand where Fort McRee used to stand.
McRee was the second of 4 forts built to defend the entrance to Pensacola Bay; it stood on the west bank of the channel between the Gulf of Mexico and the Bay.
The Confederate-held fort took heavy damage in a Union bombardment in late 1861, both from Fort Pickens and from a pair of US Navy ships anchored in the Gulf. After the war, the fort was never repaired and was left to crumble for some 40 years. The Hurricane of 1906 saw the last remnants of McRee tumbled into the surf of Foster's Bank.