One could crawl through the arteries in a blue whale’s heart.

You probably know that the blue whale is the biggest marine mammal in existence. But would you ever have thought you could crawl through its heart? Well at the very least you can crawl through its major arteries. Blue whales are so large that an adult blue whale’s heart can be almost 2,000 pounds.
It only beats once every ten seconds and the beat is so loud that it can be heard two miles away. If you’re agile enough, you could crawl right through its arteries because of how big they are. The heart is actually so big, it’s the size of a mini cooper.
Some other facts about just how big blue whales are: Their lungs are pretty big too. Each lung is the size of an average closet. Also, their tongues are so heavy that they outweigh elephants! As far as overall size goes, you've probably heard they can be as large as two city buses. Let’s just be thankful they don’t eat people.
(Source)

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