New Document and Set Up
Press Ctrl + N to create a new document. Configure the units in pixels, and set a canvas of 800x800 px. Later, in Advanced Settings, select RGB, Screen (72 ppi). Go to Preferences (Ctrl + K) and give Keyboard Increment a value of 1 px. Hit Ok.
You can open the Info panel (Window > Info) to get a preview of the size and position of your shapes. Remember to configure the units of measurement to pixels in Edit > Preferences > Units. This will increase your work speed.
How to Create the Background
Start by drawing the rectangle at the bottom of the Artboard with the Rectangle Tool (M) and use the #FBC78F color as a filling. Then, draw another one completing the Artboard with #FFEBD9 as a filling.
With the Pen Tool (P) draw in the suburbs of the town using #F0DBAB as a color filling.
How to Create the Castle Tower
Draw the rectangle of the tower (#FBB03B) with the Rectangle Tool (M) proportionately vertical. Next, draw another rectangle, seperate from the other one for the top. Later, with the Pen Tool (P), complement the space between both rectangles as we can see in the figure below. Fuse the whole tower using Unite in the Pathfinder panel.
Later with the Rectangle Tool (M) draw two rectangles to create the defence for towers. Use Minus Front on both rectangles, in the Pathfinder panel.
Now make a copy the tower (Ctrl + C > Ctrl + F) and change the fill color to #F7931E. Send them back (Ctrl+[) and with the Direct Selection Tool (A) select the nodes on the right side and move them to the right of the tower.
Later create the defence on the right side with the Rectangle Tool (M) and minus that shape on the tower.
Create the windows drawing in two rectangles (#1B1441) on the front, and another on the right side (#1B1464) of the tower. Also, draw in the balcony of the window using rectangles, on the front (#F7931E) and on the right side (#EB7D14). Later with the Direct Selection Tool (A) round the top vertexes of the windows using Live Corners.
Let's create give some depth to the windows. For this make two copies of the windows in the windows themselves (Ctrl + C > Ctrl + F) and move them slightly to the right, minus the one before (using Minus Front) and apply the fill color #1B1464. Do the same thing on the other window, but move it to the left and use the fill color #1B1441.
We'll move on to the sides of the tower's defences. Use the Rectangle Tool (M) and draw the sides on the front (#F7931E), later do the same thing on the right side using the fill color #FBB03B.
Create the top house drawing a rectangle looking to the front (#F15A24), and one looking to the side (#C74413) with a little less width to acheive a 2D effect. Duplicate the windows on the front and on the side a put them on the house.
Remember to take the shapes behind the tower (Ctrl + [).
Draw the edges of the castle using two rectangles, for the front (#FBB03B) and the side (#F7931E). Then create another rectangle on top for the roof (#7D44A0).
Later, using Live Corners, create corners with a bevel in the top nodes of the roof. With the Pen Tool (P) draw the side of the roof (#662D91).
Now draw the flag pole with a rectangle (#F7931E) and the top part with a square rectangle (#7D44A0). Draw the flag (#F15A24) using the Pen Tool (P).
Now we'll draw the entrance to the castle, to do this, create a rectangle (#F15A24) at the bottom of the tower that takes up a third of both sides. Later, create some small squares with the Rectangle Tool (M) using the Blend Tool with six copies between them to seperate them symmetrically.
Later minus them using Minus Front in the Pathfinder panel.
Draw the door and windows at the entrance in the same way we did with the first windows. Use the fill color #1B1464 to do this.
Later create the bottom edge (#CE4100) and make it go around the door. To make the door duplicate it (Ctrl+C > Ctrl+F) and apply an offset of 4 px(Effect > Path > Offset Path) and send it back (Ctrl+[). Eliminate the rest using the Shape Builder Tool (Shift + M).
Create the bricks on the wall using small rectangles (#CE4100). And add in little balconies under the windows (#FBB03B). Position the whole tower, grouping it (Ctrl + G) on the background.
Lastly, draw a road (#FBAF5D) to the entrance with the Pen Tool (P) and round off the vertexes using Live Corners with the Direct Selection Tool (A).
Fantastic! You're done!
As you can see, it was a really simple tutorial, but it's still a really illustrative and easy to do! I hope you liked this illustration and that, now, you let your imagination soar to make some similar stuff!