The small intestine is also super thin, just one and 1/2 to two inches around, almost the diameter of a golf ball, yet its surface is massive. If you flattened it out, it would be about the size ...

Wombats have unusually long and spacious intestines to compensate for their relatively low-nutrient diet of grasses and sedges, resulting in longer digestion times of between 40 and 80 hours.