What is the fine-grained topic of the following text: On 7 August the two young Germans arrived at Oban on the west coast of Scotland, and Mendelssohn made this sketch from the mainland, showing Dunollie Castle at Oban, with the village of Morven on a promontory beyond, and the island of Mull, one of the Hebrides, to the left. Only return the topic.
Mendelssohn's sketch of Dunollie Castle at Oban, Scotland