Pieces you need:

 2 large rectangles

 2 arches

2 triangles 

2 semi-circles

1 play mat

2 small rectangles

 

Steps:

TIP: As long as the playmat is on one side, feel free to arrange the rest of the pieces how you choose to create the second wall and the top of the structure.

Step 1: Turn the playmat on its thin side into a straight line to form one side of the structure.

Step 2: Place the two large rectangles on their short thin side beside each other and parallel to the first piece to form the second wall.

Step 3: Place a semi-circle in an arch and lay it beside the tall rectangles to extend the wall.

Step 4: Put the second arch on top of the structure to create a tunnel.

Step 5: Place down the remaining pieces across the top and on the side with the rectangles to complete the structure.