Survived 800 years

There are five round towers in Mayo. ( At least five that I know of!) They were defensive buildings and have survived 800 years ! Part of the defence is the placement of the main door about fifteen to twenty feet off the ground. On entering the tower the occupants pull a ladder into the tower before slamming the door shut!
This is a picture of Meelick Round Tower , You can see the entrance on the left side of the tower as you look at it.