Sculptor Sir Anish Kapoor and engineer Cecil Balmond designed the ArcelorMittal Orbit (arcelormittalorbit.com) as a visual legacy to mark the London Olympic and Paralympic Games in 2012.  Located in East London, at Queen Elizabeth Olympic Park, this extraordinary looping structure was made of 35,000 bolts and enough steel to make 265 double-decker buses. Nearly 60% of the Orbit is made from recycled steel, including washing machines and used cars. The Orbit is unbeatable for the views you get of the London skyline.Now Belgian artist Carsten H&oumlller has installed a tunnel slide in the Orbit, said to be the world&rsquos highest and, at 178m, the world&rsquos longest. In the 40-second trip, visitors will circle around the ArcelorMittal Orbit 12 times, travelling through loops and curves, including a tight corkscrew section called the &lsquobettfeder&mdashGerman for &lsquobedspring&rsquo&mdashand end with a 50m straight run back down to earth. Visitors have to buy a combination ticket for General Entry to the ArcelorMittal Orbit and The Slide (&pound15 for adults). Separate tickets can be bought for additional rides. Height, weight and age restrictions apply.