Ancient Teotihuacan

Absolute Visit not only because it is known for these enormous structures, but it's also a large residential complex with well-preserved murals and the Avenue of the Dead. The ancient city was established around 100 BC and is most famous for the Pyramid of the Sun, the largest building in the area. It's over 233 ft. high with a massive base of almost 3,000 feet. Now, that's impressive. [Source]