Designed landscape - belvedere

The National Monuments Service's description

Natural flat-topped hillock known as Windmill Hill, on the demesne landscape of St. Vincent's College, standing 240m E of Castleknock motte (DU017-012001-) and Anglo-Norman stone castle (DU017-012002-). Along with the motte, the hill is the highest point (276 ft. OD) in the landscape with extensive views of the surrounding land. Listed in the Dublin SMR (1988) as ‘Windmill Possible’, and  included in the Dublin RMP (1998) as ‘Windmill Site’.

On the summit of the flat-topped hill there is a circular stone tower (diam. c. 6m) which is annotated ‘Tower’ on all editions of the OSi historic maps.  Annotated ‘Tower’ on Rocque's 1760 map of Dublin County (Rocque 1762).   The tower (Watch Tower) was painted by the antiquarian Gabriel Beranger in 1768 who described the painting as a ‘View of two hillocks, one bearing a watchtower and the other bearing the castle of Castleknock’ (NLI, PD 1958 TX 32). The painting shows a circular tower then known as a ‘Watch Tower’ standing on the summit of a flat-topped hill with the remains of a broken out ground floor doorway and the castle of Castleknock standing on the motte in the background. The condition of the stone tower as painted in 1768 is similar to the remains of the tower still visible today.  In 1835 the Dublin Penny Journal recorded that this tower on Windmill Hill ‘was erected by Mr Guinn for an observatory, but afterwards let go to ruin’ (Anon. 1835, 236).  This watch-tower was described by archaeologist Gill McLoughlin as; ‘of mortared random rubble construction, lit by three pointed arch windows, with opposing doorways facing W and E.  No roof survives’ (Mc Loughlin 2007). 

This stone watch tower was described by the National Inventory of Architectural Heritage (NIAH) as a; ‘Ruined windmill tower, c. 1800, on a circular plan with random rubble stone walls, containing water storage unit within’ (NIAH Reg. No. 11362021).  

Geophysical survey was undertaken (Licence no. 07R0223) in advance of the insertion of a new water tank which identified a 'criss-cross pattern of potential interest' at ITM coords (708721/736533) (Nicholls 2007).  It has been suggested that this cross-like anomaly may be the remains of the site of a levelled windmill.  It is possible that the name ‘Windmill Hill’ was mistakenly applied to this hill based on the presence of the circular shaped ‘Watch Tower’ which does have the appearance of a windmill. Alternatively the ‘Watch Tower’ may have been converted into a windmill from which the hill received its name.  Or the hill was named after a medieval windmill that was levelled.

Compiled by: Caimin O'Brien

References

Anon. 1835 Castleknock. The Dublin Penny Journal, Vol. 3, No. 134 (Jan. 24, 1835), 236-7.

McLoughlin G. 2007 Archaeological Assessment at Castleknock College, Dublin 15. Licence No. 07E0682. Unpublished report, Irish Archaeological Consultancy Ltd. on behalf of CCH Architects.  

Nicholls, J. 2007 Geophysical Survey Report: Castleknock College Site Mains Water, Co. Dublin (Licence no. 07R0223). Unpublished report submitted to the National Monuments Service, Department of Arts, Heritage and the Gaeltacht

Rocque, J. 1762 An Actual Survey of the County of Dublin, on the same Scale, as those of Middlesex, Oxford, Berks and Buckinghamshire. Available at https://virtualtreasury.ie/item/LBC-Rocque-3 [Accessed 05 September 2025]

NLI, PD 1958 TX 32 National Library of Ireland, Castleknock Watch Tower, & Castle at a distance. G.B. Delt. 1768 A Collection of Drawings of the Principal, Antique Buildings of Ireland Designd on ye spot, and Collected by GL. Berenger [sic], Vol. I.. Dublin.