The best source of that information would come from the local tourist boards depending on what country region you are looking at. You could also browse the questions on wikianswers in the catergory "castles". As well as all that you could click on some of the related links listed below.
Medieval castles.
There is nothing different between todays castles and medieval time castles. Today's castles were built in medieval times.
The welsh medieval castles were big and gray.
When planning a trip to the UK, locations of medieval castles can be found by searching the National Trust organization's website, or checking a website such as TopCastles.
If you have access to google, click on images, type in medieval castles, then press 'google search'. If not, you could click on the link below named "Castle Images:google".
Medieval times
in the late medieval period many medieval castles did have a primitive type of cannon.
Castles were invented in medieval times.
There are no genuine medieval castles in the USA, because the Americas were not discovered until after the medieval period had ended. There are the "fairytale" Disney castles and some modern attempts at reconstructing medieval castles, but no genuine ones.
Who is most important in medieval history - kings and emperors. Where do they live - in castles.
There are many types of Medieval castles including concentric castles and motte and bailey castles To view more information on the different types of castles there are click on the related links listed below.
mote and bailey castles and stone keep castles and Concentric Castles