Whether you want to prevent an uprising, defend yourself against neighboring kingdoms, or just have a really unique house, a castle might be right for you. A castle owned by a feudal lord was designed to serve as an excellent means of defense from foreign invaders or just a peasant uprising. A modern day castle can serve as an excellent means of defense from door to door salespeople, or just a great conversation starter.
Find the location on which you want to build your castle. Traditionally, high ground with an excellent view of the surrounding countryside. In the modern day world, any area where building a castle is allowed by law works, but make sure you can get all of the applicable permits.
Dig the moat. This will serve as an excellent means of defense as well as making a great fish pond. The depth of the moat is up to you, however the deeper it is, the more expensive. After digging the moat, line the sides with concrete, hardened plastic or even traditional stone.
Lay the foundation for your fortress; this can be either concrete or stone. If you wish to have a courtyard or inner wall, you can either leave that area with just dirt or lay the concrete and then place dirt on top of that.
Stack the stone for the walls on top of one another, using mortar or concrete in between the stones. The sizes of the stones indicate the strength of the walls. Make sure you stack the stones in an overlapping fashion to increase the stability.
Add in features such as windows, arrow slits and door holes during the construction of the walls. If you wish to have actual glass windows, you will need to fix these in place, instead of the traditional big holes.
Construct the roof using either wooden beams or stone for more security from archers with flaming arrows. After building the roof, simply fly your flag from the tallest point and you have your very own castle.
original source: eHow.com