On 1 July 1690 (Old Style) King William III and his father-in-law King James II faced each other across the Boyne at Oldbridge, about 6 kilometres west of Drogheda. Both commanded in person, and with 36,000 men on the Williamite side and 25,000 on the Jacobite side it was the largest army ever gathered on an Irish battlefield. James lost, fled to France, and the outcome shaped Ireland, Britain and Europe for centuries.
The visitor centre is on the Oldbridge estate, on the battlefield itself. Oldbridge House was closed at the time of writing, and the exhibition, with original weapons and a laser model of the battle, is in the adjoining stable yard. The grounds, walled garden and battlefield walkways are free. Allow about 45 minutes for the exhibition and an hour for the walks; it combines naturally with Brú na Bóinne, a few minutes up the road.