Close to Taupo is Huka Falls. It's one of the main attraction here. Waikato, 100 m wide, squeezes through a 15 m wide channel, and tumbles down 11 m.
It was a bit funny, watching boats and Jet boats approaching the fall, like Niagara Falls or the Rheinfall, which have a total different dimension.
Apart from that, it's a nice hike along the incredible blue river to the white rushing water before the fall. It's a 3 km hike one way.
And after the hike, take a hot dip in the Otumuheke Stream in the Spa Park. It's right at the begining of the hike, when you meet the river Waikato.