Perth and Kinross: See
Castles: mostly made-over in Victorian times, such as Scone Palace near Perth, Blair Castle in Blair Atholl, and Drummond Castle near Crieff which you can't go inside but come for the gardens. There's more antiquity at Elcho Castle near Perth, and at Loch Leven in Kinross where a rowboat takes you out to the island castle that Mary Queen of Scots escaped from.
Wildlife: beavers have been re-introduced to Britain around Loch of the Lowes above Dunkeld: they're thriving and spreading throughout the river valley. Lots of red deer and other wildlife, including plenty of eagles, though most tourist sightings turn out to be buzzards or hawks.
Scotland's Gardens opens up private gardens once a year in summer, with all proceeds going to charity. There are about 20 participating gardens in this area, dates staggered so there's one open most weekends.
Autumn colours are brilliant in this area; see them anywhere around Perth, Crieff and Aberfeldy. They're excellent in the Hermitage glen above Birnam, but get there by midday, as the glen loses its sunlight by early afternoon.