Urquhart Castle has been a ruin since the 17th century and the ruin is spectacular. The castle sits on a rocky promontory jutting into Loch Ness, with a five-storey tower house still standing and views up and down the loch that are among the best in the Great Glen. In the late afternoon, when the tour buses have gone, the light on the water and the old walls is close to perfect.
The visitor centre has good historical context. Allow 90 minutes minimum to walk the full site. The car park fills early in summer, arrive before 9:30am or after 3:30pm if you want space and relative quiet.