Why is the pool at Buckingham Palace a secret?

3302.977 - 3325.294 Garrett Graham

Like my assumption is you're inside the pool and you can look out on the beautiful back gardens of Buckingham Palace, but from the outside, you cannot see anything. Like the panes just look like ink-stained squares of glass. which was honestly so tantalizing. Like a quarter inch of glass is what was separating me from the answer to this question that I had been thinking about for months.