Caisleán Bhaile an Ásaighis aka Ashtown Castle is a medieval 4-storey tower house in the Phoenix Park. It is thought to date back to the 15th century (as it is built to dimensions that conform with a government policy of the time that offered £10 to those who constructed a castle for their own safety).
- In 1641 the castle was owned by John Connell or 'John of Ashtown' as he was known. The estate was then 200 acres laid down to arable and pasture land with a small area of woodland, there was also a small orchard and two thatched cottages on the estate.
- In 1668 Marcus Trevor, Viscount Dungannon along with two keepers were the residents of Ashford. The castle had been acquired by the Lord Lieutenant of Ireland on behalf of the King to extend his deer park.
- Around 1774, the castle was incorporated into the construction of the Georgian mansion known as Ashtown Lodge aka the Under Secretary's Lodge (from 1782). A series of tunnels ran from the lodge to other important buildings within the park.
- It later became the residence of the Papal Nuncio up until the building was demolished in 1978 due to dry rot. It was only then that the original tower house was discovered hidden within its walls.
Ashtown Castle has now been restored with the floor-plan of Ashtown Lodge marked out using hedgerows. The Victorian walled garden and stables are also open to the public. They can be found adjacent to the Phoenix Park Visitor Centre.