On the US side, there are several fun activities. My favorites were Cave of the Winds and a boat from the Canadian side (rather than the expensive Maid of the Mist). The view of the falls is also better from the Canadian side, so make sure to bring your passport and keep it with you. The falls are also lit up at night, so plan to visit during the day and night.
Cave of the Winds
You get up under the falls by just walking down some wooden stairs, which I thought was much more fun than approaching by boat. You are given a "souvenir" rain poncho and surprisingly sturdy sandals. You will get wet. You are also unofficially guaranteed a selfie opportunity with a rainbow.
Tickets are only available on the same day, in person at the park.
It can get quite crowded on the decks, but I enjoyed it nonetheless.
Sandals are included in the price, because you will get wet.
Guaranteed rainbow picture.
You can practically lean into the falls from this point on the Canadian side.
Sunset is gorgeous from the bridge between the US and Canada.
Fireworks shows are held daily during the summer.
