IMPISHLY EXCITED IS perhaps the perfect way to describe a traveler journeying through Scotch whisky country in midsummer. With days that draw out long into the evening, mild weather and wild, high-mountain beauty, it's not difficult to see how a generation of Romantics fell for the Highlands. The A9 runs through its heart: Once past Perth, it approaches the middle of Scotland, then swings northward past Loch Garry, climbing more than 300 meters to the northern shores of Loch Ericht.

At this point, whisky lovers will crane their necks to catch a glimpse of Dalwhinnie. By no means the first distillery in this, the largest Scotch whisky region, it nonetheless stands as a landmark, beyond which lie the mountains of the Cairngorms and Speyside.

Unlike Islay or the Lowlands, the Highlands are so vast—more than half of all single malt whisky is produced here—that it's difficult to think of one overarching defining characteristic.

One could argue that Highland malts are characterized as big and full-bodied. Certainly, the further north you travel, the sweeter, more powerful and more complex the whisky becomes. As a rule of thumb, the eastern Highlands produce gently peated, slightly drier malts; Speyside's are the sweetest; and in the west, the malts are peated but don't take on the overwhelmingly pungent, phenolic character of Islay malts.

Which leaves the islands—not a category recognized by the Scotch Whisky Regulations 2009, but a term that whisky writer Charles Maclean says is commonly used by retailers and publishers. This collection of distilleries, which includes some of the most picturesque spots on the Scotch whisky trail, is made up of Tobermory on the Isle of Mull, Talisker on the Isle of Skye, the Arran distillery on Arran, Isle of Jura on Jura, and Scapa and Highland Park on the Orkney Islands.