I was visiting my friends' house in the Hollywood Hills, and noticed a built-in niche under the stairs in the living room. My friends don't know what the niche is for.
The house was originally built for Jean Harlow in the 1930s. When I tweeted these photos a couple of days ago, my twitter followers replied that the niche might have been built to hold a champagne bottle and a couple of flutes, but we tested that and a champagne bottle won't fit.
Other suggestions included: a place to hold the mail (not deep enough for mail), film awards (seems too small), candles (fire hazard), glove warmer (not in southern California), milk bottle holder (weird location for that), martini shaker holder (that would be better in the bar), phone (too small), pneumatic tube station (in my dreams).
None of the above guesses seem right. What do you think it is?