Once you’ve entered the park from one of the five gates, it’s important to keep in mind how truly vast Yellowstone is. The world’s first national park is 2.2 million acres, or more than 3,400 square miles. That’s bigger than the countries of Luxembourg and Singapore combined, or larger than the U.S. states of Delaware and Rhode Island combined. It’s not a park you can see all of on foot, or even by car, in a single day or even a week.