Just outside Agra is Fatehpur Sikri, a large settlement from the 16th century that was capital of the Mughal empire, built by Akbar the Great. It was abandoned not too many years later. It's also a UNESCO site.
Most buildings in the complex have incredible carvings, and there's influence from Muslim and Hindu architecture. There's a mosque and some tombs and palaces here.
If you see that tower in the distance, it's supposedly in tribute to Akbar's favorite elephant, and it's made of elephant tusks.
Akbar had a lot of wives, and his three favorites got their own palaces. They were each of different religions, and he was cool with that and built their palaces accordingly. And the wife who got the smallest one got the most beautiful one.
Some of the abandoned structures on the way out. Some theories think everyone left because of lack of water.
Next stop - Agra Fort! The second UNESCO spot of the day. This one was also designed by Akbar the Great as a military structure, then another emperor - Shah Jahan - made it into a palace, where he was later imprisoned. Shah Jahan is also the creator of the Taj Mahal, which you can see from here. I recommend visiting this spot first.
I'll never get over all the detail here and pretty much everywhere I went in India. It's marvelous construction.
What's that I see over there? Oh, just one of the most famous buildings in the world. Maybe the most famous?
Lots of palaces around here. Eventually they start to run together.
Somewhere in here is where Shah Mahal was imprisoned for eight years. He had fallen ill, his sons had a squabble over who should take power, and when he recovered from his illness, his son put him under house arrest. He had a private mosque in this area of the fort, and one of his daughters also stayed with him. He died in this condition, and then was buried next to his wife in the Taj Mahal.
Monkeys are scary, by the way. Stay far away. They'll steal your stuff, bite you, and attack your children. Not a joke.
Agra Fort is definitely recommended. There's a lot of good history to learn in here, and it's so tied to the Taj Mahal. Come get the full story.