This post shows some of the architectural details of the castle.  The staircases in the towers were interesting.  These were made with wooden treads which could be removed and replaced when they wore out, a classic feature in medieval architecture:

These stairs were pretty cool.  Walking up and down them, it was easy to imagine myself someone who lived in the castle at that time, wandering through those spooky towers:

I loved the way the brick stairs had worn down so much over time:

This door led into a room where someone had been kept under the medieval version of "house arrest" for a while:

This staircase led from the bottom of one of the front towers up to the level where the knights would shoot out at attackers:

This fireplace was in the bridge master's quarters:

This room was used for defense, and for storing cannons and cannonballs:

Here is a sentry walk which was originally open, but later roofed-in.

This is one of the niches that small cannons were fired from.  You can see the three-foot thick walls clearly in this picture:

This unique construction in one of the tower roofs is worth mentioning.  There are two sets of eight beams coming into the centre from the outside edges of the tower.  They connect to one, central beam which is not attached to anything else.  It is a "floating support beam." 

In one of the towers, these massive beams were embedded into the brickwork of the walls in an attempt to prevent the structure from leaning.  Unfortunately, it didn't work and later, the walls had to be reinforced with a concrete corset. 

In one of the larger sentry walks, these horizontal beams could be moved in or out.  When pushed out, they were used to make scaffolding outside:

This is the best example of the curved beams seen all over the castle.  Creating them was a huge feat during those times: