The basalt is the bedrock, but it was the glaciers of the last Ice Age that gave the Antrim Hills their distinctive shape. Where rivers and rain have rough, jagged work, ice does something gentler. It planes the tops flat, rounds the shoulders, and scoops out the valleys with broad U-shaped curves. That is why the nine Glens of Antrim, which radiate down the eastern edge of the range, have such a soft, sweeping geometry, and why the high ground above them looks more like a quilt than a saw blade. The summits do not stab the sky. They hold it up like the back of a hand.

Trostan is the king of the range at 551 metres, the highest point in County Antrim and one of only four mountains in the Antrim Hills that qualify as Arderins, the Irish category for peaks above 500 metres with significant prominence. From its top on a clear day, the whole of the Glens unfolds to the east, Rathlin Island floats off the north coast, and the Mull of Kintyre across the North Channel reveals just how close Scotland actually is. Beyond Trostan, the rest of the twelve highest peaks step downward to the south, ending near Belfast where Divis Mountain rises over the city as part of the Belfast Hills rather than the Antrim range proper.

Most of the range is moorland and blanket bog, a habitat that looks empty until you stop walking and listen. The peat under your boots has been growing for thousands of years, one millimetre at a time, soaking up rain and locking away carbon. Heather purples the hills in late summer, bog cotton waves in the wind in early summer, and in the still air after rain the whole plateau smells faintly of wet thatch. It is sparsely populated country. The villages crowd into the lower glens where shelter and water are easier, and the high ground is given over to sheep, to birds, and to the kind of silence cities forget exists.

The wildlife of the Antrim Hills runs the full vertical scale. On the ground, red foxes hunt the moorland edges, pine martens have been quietly returning to the woods on the lower slopes, and red squirrels still hold on in the conifer plantations where their grey cousins have not yet pushed them out. Above, the air belongs to peregrine falcons, buzzards, and sparrowhawks. A peregrine in stoop is one of the fastest animals on the planet, and the broken cliffs of the Antrim escarpment give them perfect nesting ledges. Watch one drop from a cloud onto the moor and you understand why local pigeons keep their wits about them.

The range is officially designated an Area of Outstanding Natural Beauty, the same protected status used across the United Kingdom to safeguard landscapes that fall just short of national park designation but are too important to leave unguarded. Walkers, climbers, and drivers of the famous Antrim Coast Road all benefit. From the road on a fine afternoon, the hills rise on one side and the sea drops away on the other, with the glens cutting like fingers from the high ground down to the water. From above, in a small aircraft on the way to or from Belfast, the same view widens into something even better: an entire range of green-and-brown hills standing braced against the North Channel, with Scotland a clear line on the horizon.