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Photo: Guliolopez (Wikipedia:en:User:Guliolopez), CC BY-SA 3.0 via Wikimedia Commons
This grand Folly is a 135-ft (38-m) turreted tower, completed in 1859 as a memorial to Charles Vane, 3rd Marquess of Londonderry. It's in Scottish Baronial style imitating a pele tower, and the interior is occasionally open. It's built over a prehistoric hill fort, of which nothing remains. You mostly come for the view from the hill, and the surrounding country park.
Scrabo Tower is a 135 feet (41 m) high 19th-century lookout tower or folly that stands on Scrabo Hill near Newtownards in County Down, Northern Ireland. It provides wide views and is a landmark that can be seen from afar. It was built as a memorial to Charles Vane, 3rd Marquess of Londonderry and was originally known as the Londonderry Monument. Its architectural style is Scottish Baronial Revival.
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The most terrible loss of life in the First World War was on the Somme in 1916, but this museum commemorates Ireland's role throughout that war. It's a guided tour, usually on the hour. They also manage the Ulster Memorial near Thiepval, midway between Amiens and Arras, where the Ulster Division captured the German Schwaben Redoubt.
Grand 19th-century house and gardens, the lavish creation of the 3rd Marquess of Londonderry. Having spent £150,000 on the makeover of what had been a Georgian mansion, he fortunately had £30 spare to donate to famine relief. He's the fellow commemorated by the Scrabo Tower; he also has a fancy statue in Durham where he furiously opposed laws against child labour down his coal mines. Mount Stewart slumped under later descendants until revived by the 7th Marquess, then it passed to the National Trust.
Substantial ruin of a Cistercian abbey founded in 1193, with a small physic and kitchen garden. The exhibition centre is only open Feb-Nov Sa Su 1-4PM, but you can stroll around the ruin any time in daylight.