Volksgarten is one of central Vienna's easiest garden stops, set beside the Ringstrasse and the Hofburg. Its rose beds are the main pleasure in season, with old plane trees, formal paths, and the neoclassical Theseus Temple giving the park a calm imperial frame.
It is not a destination for a whole afternoon, but it fits naturally into a walk between the parliament, the Hofburg, and the museum quarter. Come in late spring or early summer if you want the roses at their best.