A round-the-world adventure exploring curious worlds hidden beneath our feet, from underground burrows to ancient cities and shopping malls. Fourth book in the successful Walk this World series. This stunning lift-the-flap book takes the reader on a journey all around the globe and deep underground. There they'll find amazing hidden worlds, teeming with life - from prairie dog towns and ant cities, to opal mines and treasure-filled tombs. Each spread is bursting with details and has new surprises to discover in the cutaway artwork and under the flaps. With so much to see and explore, this is a perfect gift for young adventurers.