Scrabo Tower (Londonderry Monument), Scrabo Hill, Scrabo, Newtownards, Co Down, BT23

Scrabo Tower is a tall square tower erected in 1857–58 on the summit of Scrabo Hill, west of Newtownards, to commemorate the 3rd Marquis of Londonderry (1778–1854). Designed by Charles Lanyon, with evidence suggesting the design was actually by his partner William Henry Lynn, the tower stands approximately 42 metres high and is one of Northern Ireland's most famous landmarks, visible for many miles around due to its prominent hilltop location.

The tower is built in the French-influenced Scots baronial style. It consists of roughly six storeys constructed in random basalt rubble with Scrabo sandstone dressings to most openings. The base comprises a tall battered plinth. The top of the tower features castellated and corbelled battlements with small round corner turrets, each topped with steep stone conical caps to the north-west, north-east and south-west corners. Within the battlements sits a large central tower with a similar steep conical roof, topped with a beacon for aircraft at its pinnacle. Projecting from the south-east corner is a full-height round staircase turret, also with a steep conical roof.

The north face is entered via stone steps leading to a semicircular-headed recessed doorway with a diagonally timber-sheeted door and wrought iron security grill. Above the doorway is an inscribed panel dedicating the tower to the 3rd Marquis, followed by a recessed sandstone panel bearing a coat of arms. Four centrally-placed windows rise above this, one directly above the other with a large gap between the lowest and the next window up; all have metal sash-like frames with many small panes. Small slit windows flank the main doorway with matching windows directly above. The east face has four centrally-placed windows arranged similarly, though the lowest window sits at an even lower level, with two small slit windows below it and one to its left, plus two more above. The south face contains four centrally-placed windows in the same arrangement as the north face, plus a fifth similar window on the battered plinth at ground level with a slit window to its right. The west face has three centrally-placed windows at upper levels only, with two slit windows on the plinth below and two more at a much higher level above. The projecting stair tower features six slit windows at various levels facing roughly south-west, five windows facing roughly south, and five more facing roughly south-east. A slim slightly projecting course marks where the stair tower meets the corbelled battlements, above which sits a series of windows around the tower and a door accessing the battlements, just below the conical roof eaves. Each small corner turret has a slit window and a doorway to the battlements.

The tower's conception arose from a group of admirers who met at Newtownards rectory in July 1854 with the aim of building a memorial in the town square. In 1855, the decision was made to site the memorial instead on Scrabo Hill and to select the design through competition, with a cost limit of £2,000. Lanyon's design, or that credited to him, placed third or fourth but was accepted because it fell within budget. The foundation stone was laid on 28 February 1857 in a well-attended ceremony. To save costs, the height was reduced by one storey from the original plan, yet the final expense reached £3,010. The contractor, Hugh Dixon of Newtownards, was reportedly ruined by the scheme, and there appears to have been little press coverage upon completion, which occurred in late 1858 or early 1859.

The plaque above the entrance states the tower was inspired by gratitude from the local tenantry towards the late Marquis for his concern during the famine. However, the vast majority of tenants did not subscribe; over two-thirds of the cost was paid by 98 individuals, headed by Emperor Napoleon III, predominantly fellow gentry from Antrim and Down and personal friends of the Marquis. In reality, the 3rd Marquis had alienated much of his tenantry through his unyielding stance during the Tenant Right campaign of the early 1850s. Historian Trevor McAvery has characterised the tower as a symbol of landlord power, a constant visual reminder of authority over the surrounding parishes.

The tower was occupied by caretaker residents from the Millen family until approximately 1966. After a period of neglect, the structure came into the care of the Department of Environment and underwent sympathetic refurbishment in the early 1990s.