Niagara Falls is among the most popular destinations in North America, and, in a way, it's two destinations in one. The enormous waterfalls are on the USA/Canada border, and there are towns with the name "Niagara Falls" on both sides. Each provides a different view of the rushing water, and thankfully it's easy to move between the two, so no matter which one you decide on as your home base, do yourself a favour and visit both.
The Canadian side of Niagara Falls, located in Ontario, is reputed for having the best views of the waterfalls themselves. The American side, in New York State, is the country's oldest state park and therefore less built-up. Visited together, they represent a long-standing honeymoon hotspot - Niagara Falls hotels are notorious for features such as beds shaped as hearts, and bathtubs that look like huge champagne glasses - but that's far from the only reason people visit the area.
In addition to viewing the massive waterfalls themselves, the area around the Niagara River is great for hiking and enjoying the natural beauty during the summer months. On the American side, Niagara Falls State Park includes other attractions as well, including Goat Island (in the middle of the Niagara River between two of the waterfalls) and the observation tower at Prospect Point Park. During the high season, the Canadian side of the falls launches fireworks every night and if you spend a few days in the area, you can test both sides of the border for the best view.
The airport nearest to Niagara Falls is on the US side of the border in Buffalo, New York. Once at Niagara Falls, you can visit both sides of the border without a car - there's even a bridge you can walk across (just don't forget your passport!). Should you want to explore the area further, however, renting a car is a good idea.