[1][2] Scrabo is pronounced /ˈskræboʊ/ according to the British Broadcasting Corporation (BBC)[3] or /ˈskrɑːboʊ/ according to the pronunciation heard on the Placenames Database of Ireland website.

[5] The Northern Ireland Place-Name Project derives the name from Irish screabach meaning "thinly covered rock"[6] or "rough stony land".

His second wife was a rich heiress and the marriage contract obliged him to change his surname to hers, which explains why he was first called Stewart and later Vane.

The estate's great house, Mount Stewart, became his Irish residence but after his second marriage he lived mostly in England.

The local gentry and the late marquess's friends, among which Napoleon III of France, donated most of the money, with some of the tenants also contributing.

At first, the monument was to be built in Newtownards, but it was later shifted to Scrabo Hill where it could be seen from Mount Stewart and where suitable building stone was quarried.

When the committee called for tenders from building contractors, all the submissions for the three best-rated entries exceeded the budget and were therefore rejected.

The 5th Baron Dufferin and Claneboye, a neighbour of the Londonderrys, had recently built Helen's Tower, also in the Scottish Baronial style, on the next hill to the north of Scrabo.

[citation needed] A gilt-framed picture of the Scrabo Tower, which seems to be a coloured-in wood engraving, is preserved at Mount Stewart.

It gives an artist's view of the Londonderry Monument, showing three towers linked by two short stretches of crenellated wall.

Wood engravings similar to this picture have been published in the Illustrated London News[23][24] and the Dublin Builder.

[25] The foundation stone was laid on 27 February 1857 by Sir Robert Bateson and blessed by the Church of Ireland bishop of the diocese on demand by William Sharman Crawford, chairman of the Building Committee, in a ceremony attended by the 4th Marquess, his wife, many members of the gentry, and a crowd of residents and tenants.

[29] Those loyal to the Stewart family suggested the inspiration for the memorial lay in the gratitude of his tenantry for the solicitude the Marquess had shown during the Great Famine.

Londonderry refused to consider rent reductions, had objected to public works schemes for famine relief,[30] and while making contributions of £30 to the local soup kitchens in 1847, spent £15,000 renovating their home in Mount Stewart.

[32] Two thirds of the cost of the tower was met by 98 subscribers (in a list headed by Emperor Napoleon III) most of whom were fellow gentry.

[39] The tower now stands in the Scrabo Country Park, which is managed by the Northern Ireland Environment Agency (NIEA).

[40] In 2014, the NIEA announced that water ingress had damaged the electricity supply, and citing safety concerns, closed the tower to visitors.

The tower's square part is surmounted by a short setback cylindrical storey that is covered with a steep conical roof.

The transition from square to round is achieved by a platform decorated with four corner turrets linked by machicolated battlements.

The southeastern turret serves as cap-house over the stairs giving access to the parapet walk (or chemin de ronde).

Erected in memory of Charles William Vane 3rd Marquis of Londonderry KG & c by his tenantry and friends

Fame belongs to history, remembrance to us 1857 Above the plaque is a recess filled with a relief in white limestone or marble showing the coronet, two crests (dragon and sword arm), and the motto of the marquesses of Londonderry.

As the area to the south and southwest of Scrabo Hill is part of the Ulster Drumlin Belt, this glacial landform can be very well observed from the tower.

On clear days Helen's Tower in the north, the Copeland Islands with their lighthouse and the Scottish coast (Mull of Kintyre, Ailsa Craig and Rhins of Galloway)[9] beyond the North Channel in the northeast, the Isle of Man in the southeast, the Mourne Mountains in the south, as well as Divis Mountain and Cave Hill over Belfast in the west can be seen.

[55] The eastern part of the hill is of geological interest because outcrops in the South Quarry reveal contacts between sediments (sandstone) and locally cross-cutting sills of intrusive rocks (dolerite).

This eastern part, which includes the site of the tower, has been declared an Area of Special Scientific Interest (ASSI).