The ones that were organized as Mont and Bailey castles usually still do because they began with walls, but there are castles with no walls. I can think of several that I have been to in Germany. Peterhof in Russia built by Peter the Great has no walls, but does have extensive gardens. The Hermitage also in Russia was the winter palace of Catherine the Great has no walls. Linderhof in Germany has no walls. Many castles and palaces we see today are rebuilt and remodeled by various people through the centuries.
Tapestries and other decorations would have been hung on the walls of medieval castles. Additionally, animal heads and other trophies captured by the lord of the castle would have been displayed.
A castles main defense were it's high stone walls and sometimes a mote, a channel of water
Medieval castles were needed for safety because they protected people from invaders and other dangers. Castles were also built to defend from danger. They were equipped with high walls, murder holes, cover for soldiers, and more.
Medieval castles.
There is nothing different between todays castles and medieval time castles. Today's castles were built in medieval times.
Medieval castles were usually made of stone, often held together with mortar. Some castles were made of wood, and earth was also used in the construction of some castle defenses and walls.
The welsh medieval castles were big and gray.
Medieval times
in the late medieval period many medieval castles did have a primitive type of cannon.
All of them lived in several castles.
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.