OK I did my first four tier cake for my sister in laws wedding. It was in the fridge all night at the hall and I took it out at 11:30 that morning. Reception was at 5. By the time we got to the reception, the whole back of the cake was sinking. I dont know if it was due to the temperature of the room (it was fondant) or that the cake itself was heavy? Does anyone have any insight I would greatly appreciate

What kind of cake was it? Scratch, mix or fruitcake or what?
And as was already asked - what kind of support did you use?
We really need much more info to try to help you.