A houzz contributor, not too long ago, had made a wine rack out of 4'x4' wooden pallets, that are used in the US to move a load of goods with a fork-lift truck. Perhaps they have them in your country. He cut them in half so they were only two feet deep and stacked them up to high counter height. The wood would be a nice contrast with your concrete, might add a little warmth to the space. cascio.offsite@gmail.com

The places I'd actually put a fridge: 1) The main one in the kitchen for everyday use. 2) a spare in the basement near the TV room for snacks & drinks when people come over to watch a game or teens are hanging out. Also used as extra storage when buying things in bulk or when preparing Thanksgiving dinner. 3) possibly a spare in the garage for drinks when I'm working outside and don't want to track dirt/grass into the house from the garden. 4) a small one in the dorm room at boarding school or college.

cool --but you can see the entire floor has been raised--do you have the ceiling height? a closet 'step up' would be less of a structural commitment, OR a buildup under builtin furniture--like bookcases flanking a fireplace, also some great ideas on HOUZZ i'd never have thought of. sorry i'm not tech-ie enough to paste the site:) of course if you go 'structural' --all walls and ceilings are fair game as well. remember that ease of access [or lack thereof] can affect stealth mode greatly--as in your pic: every time you step onto the 'box' in your pic you would hear a 'different' sound.

Better to open both the doors... make a sliding door. Better than a mirror look for clean half white colour paint or laminate for wine storage above. Put more of ceiling lights to see highlight the niche for easy working. dim light are only used where a person is seating to have his drink and not at the place where he store the bottles...