Glamis Castle
In fame, among Scottish castles, Glamis is second only to Balmoral. It has a fresh royal connection (as the Queen Mother's childhood home) and a ghost.
It was the only castle where we took a guided tour inside. We had no choice. It was a bit crowded that way, and slow. We got more information than we wanted about the royal family.
We saw the room where the fictional MacBeth murdered Scotland's king. The guide said there was a real king named MacBeth whose reign was long and peaceful.
The gardens were Italianate in style (ho hum), and there was a charming pet cemetary near the gate.