A castle front, with a working draw bridge. You can even go further and add a moat filled with water, but this is better done outside!
Step 1: The first tower’s base.
Build three sides of a 8×8 tower, 6 layers high. Once the walls are built, you can add a door in the empty space (we used a cell door), then add small plates for the floor of the next level.
Step 2: The first tower’s first floor.
The first floor is little bit different: it is only 5 layers high and it has 3 windows.
Start by laying the first layer. Then build 2×2 pillar, 4 layers high, on the left hand side. Leave 2 spaces empty for a window, then build a 4×2 pillar, 3 layers high. Do the same on the opposite side. Add a 6×2 block to complete the side walls.
Then, use small plate for the next floor, but attach a 4×2 brick that will serve as the top brick of the front window.
Step 3: The first tower’s second floor.
The next floor also has a window on the right and front sides, but it has a door on the left side.
In the first layer, start with a 2×2 cube on the left far side, leave a 4×2 space empty, then complete the layer. Complete the walls, the right hand side one being the same as the previous floor, the right hand side one having 2 2×2 pillars topped by a 8×2 brick.
Add small plates for the floor of the next level.
Step 4: The first tower’s third floor.
This floor is the opposite of the previous one: there is a window on the left hand side and a door on the right. There are also a few key differences:
It is 7 layers high.
On the 1st layer, instead of using a 2×2 square on the right far side, use a 4×2 brick with half of it going out of the tower (red block below, we will use it later to attach a bridge).
On the 5th layer, on the front right side, use again a 4×2 block going half outside (orange block below) with a 1×2 brick.
Add 2 8×2 bricks on top of the two sides.
On the final layer, we will use 4 2×2 roof bricks that go towards the outside (see bottom picture below).
Step 5: The first tower’s top.
Using small plates, build the top floor platform. It is larger than the other floors, 10×12.
On the far right side, place a brick with a hole.
Build the top wall, 2 layers of brick toped by a third layer a 2×2 squares.
Place a long cross axle in the brick with the holes. At the end, add round bricks with cross holes in the middle. These will be used to connect to the second tower.
Step 6: The second tower.
The second tower is identical to the first, only mirrored: the second floor has a door on the right side instead of the left; the third floor has a door on the left side; on the top, the brick with the holes is placed on the far left side.
Place it 16 knobs away from the first tower.
Use the round bricks to connect the cross axles of both sides.
Step 7: Completing the towers.
Using plates, build a 6×16 platform that you will use to create a bridge between the towers on the third floor. Use the bricks going out of the tower to help with attaching it. Then, add bricks on the sides to build a small wall.
At the bottom of the towers, place 2 2×2 squares.
Step 8: Building the side walls.
At the bottom of the side walls, use sloped bricks and add a pillar going up to the top of the first floor a few blocks behind.
Build a wall of small bricks, 7 layers high.
Top it with plates, using the pillar as a support.
Build a small wall on the platform.
Repeat the same process on the other side.
Step 9: Building the draw bridge.
Take a large 16×16 plate.
On the top, attach 4 2×14 plates. Attach more plates behind, horizontally.
Finally, on both sides on the top, attach 2 pieces that you will use to connect the rope. We used 2 2×2 coupling plates, but you can use any piece that has a hole.
Step 10: Attaching the draw bridge.
All you have to do then is to attach one side of the ropes to the axles between the towers and the other side to the draw bridge. Use the two pieces protruding from the towers to hold the rope on the side. Use the round pieces to turn the axles and move the draw bridge up or down.
Bonus step: The moat.
You can complete the castle by building a moat. However, I would recommend doing it outside, as there is a risk the water will spill out.
To do so, use a box to raise the castle. Then, using Duplo blocks, build a large rectangle on a plate, 3 blocks high and empty in its middle.
Put a waterproof film in the inside of the rectangle. Be careful when doing it, so as not to tear the film.
Add water: you now have a moat over which you can lower your draw bridge!