The Trollhättan Falls are the reason the town exists — a point where the Göta River once dropped 32 metres through a narrow rocky gorge in one of the most powerful waterfalls in northern Europe. Today the river is almost entirely diverted through the adjacent hydroelectric power station, and the gorge runs dry for most of the year. The exception is the annual "waterfall days" (Fallens Dagar), usually held in July, when the sluices are opened and the full flow returns — a genuinely spectacular event that draws visitors from across western Sweden.
Even without water, the gorge is worth visiting. The basalt rock walls are dramatic, the old canal lock system (with its staircase of chambers from different eras of engineering) runs alongside the falls, and the surrounding park has information about the hydroelectric history. The 1908 power station building downstream is preserved and sometimes open for guided tours. The walk along the gorge takes about an hour and can be combined with a visit to the Innovatum and Saab museums nearby.