Finally we have a first class TB Hotel at Madrid Barajas International Airport. It's a 24 cm - 17 cm - 6 cm plastic container.
The Cache is in walking distance from Terminal 1, 2 and 3, ground level. Follow the signs to the metro station, VIP parking and P2.
If you arrive in Terminal 4 or 4S you will have to take the shuttle bus to Terminal 1, 2 and 3. Please consider that this will take a while. Don't miss your flight. Leave the bus at T3.
In order to avoid unnecessary stress and frustration I tried to make the find as simple as possible. Let me know if there's something wrong.
Please make sure that there is always at least one TB in the hotel.
Safe travels, happy hunting!
22 APR 2014: cache reactivated, a big thank you/Dankeschoen to MoeMK