Build a working mechanical model of London's iconic Tower Bridge, complete with horizontal walkway and bridge sections that raise and lower when you turn a crank. Pop the laser-cut sanded plywood pieces out of the sheets and follow the included instructions. Small has 226 pieces; finished size 11"w x 7 ½"h x 3"d. Large has 312 pieces; 21"w x 14 ½"h x 6"d. No glue needed. Ages 14 and up.