Leith Hill is the highest point in southeast England, a wooded Surrey Hills summit crowned by an 18th-century Gothic tower. Climb the tower and the view opens far beyond the immediate woodland: across the Weald, toward the South Downs, and on a clear day as far as London and the Channel. It is a proper countryside outing rather than a quick town-centre stop.
From Guildford it works best as a half-day trip by car, bike, or a carefully planned walk using local paths and buses. The hill is especially good if you want the Surrey landscape itself, not just another historic house. Wear shoes that can handle mud, and check National Trust access details if the tower climb matters to you.