Sir Thomas Makdougall Brisbane built an astronomy observatory at his birth home, Brisbane House, Largs in 1808.

In order to establish a true North South line in the sky which would enable him to make accurate telescopic measurements, he built three stone marker columns on top of Greenhill in the Halkshill area of Largs. These are known locally as The Three Sisters.

He also built a cylindrical meridian pillar in a field, mid-way between Brisbane House and the Three Sisters. Aligning all three, he established a fixed line in the sky, which he could use to study the stars.

There is an information board in Waterside Street, Largs in front of Greenhill, which gives you more detail. There is also a flight of stairs (under the trees on the left) which lead you up to the three meridian pillars.