Quebec's largest waterfall Montmorency is only a 15 minute drive from the city along the river to the north. These falls, which are taller than Niagara, are splendid in the summer, but especially so in the winter when they freeze over, causing a large steam plume and frozen "sugar loaf" at the base. There is a cable car that you can take for a close up look, or a zipline for an even closer one. You can also walk across a footbridge across the fall line. There's also a set of steps walking down the side that lead to nice views as well. In the winter, the stairs and zipline may be closed when it is icy. The falls are magnificent and well worth a quick day trip from Quebec city.