Last year, when we were taking apart the garden to go into its winter dormancy, Himself dug out some watermelons. Most of them were the normal sized ones, and most of them were past their "sell by" date and ended up as chicken food. Much to the chickens' delight! However, we did end up with one prize winner! It weighed in at 40LB! (18kg for my metric readers.)
Even bigger than our microwave (it was blown, so it was outside in the garage to be taken to recycling.)
Really difficult to measure something that rocks in weird shapes, but we think it was 23"/58cm long
And about 13"/33cm across at the widest point.
I forgot to take photos of the inside... oh, bite me!... because it was so yummy, I just tucked in and didn't think about pics. The most glorious rich golden yellow, sweet and juicy! Our neighbors each got a quarter. Best. Watermelon. Ever!