Yellowstone National Park

If you are looking for a place to visit in US and you have not already been to, you should consider Yellowstone national park in Wyoming. It is an enigma with numerous geysers, hot springs, colorful pools, fumaroles, mud pots, canyons, lakes and waterfalls. Unfortunately the park is buried in 50 feet snow in winters so summer is the only time to go. It is extremely hot in summers so don't forget your sunscreen & hat, ah! and also mosquito repellant (I don't want you to get red scars like me). The park has a couple of thousand geysers, some very faithful ones which erupts right on time and others for which you will have to wait long like 50 years ;). You will smell Hydrogen sulphide (rotten eggs) most of the time in geyser basin (one of the areas in the park) and also get a free warm sulphur bath at a couple of places but it is totally worth it.

The park also has a variety of wildlife. Some animals like Bison are abundant like mosquitoes. If you want to photograph or see a Bison closely, drive to Lamar valley. A few of them can also be seen in Old faithful geyser basin but it's better not to waste time for them in the geyser basin when it is hard to avoid them in Lamar valley. You can also spot Pronghorns, mule deer and elks in Lamar. Do remember to carry your binoculars. I was able to spot a wolf high up on a hill using mine.

There is a park Grand Teton National Park adjacent to Yellowstone and the same permit/ticket allows you to see both the parks but trust me it's not worth it, try to spend an extra day at Yellowstone instead.