Tower Bridge glass walk

On the 120-year-old Tower Bridge in London, England, a glass walkway has been installed that allows visitors to see down to the River Thames 138 feet below. The walkway, itself, is 36 feet long and six feet across.

Access to the walkway is included with admission to the bridge — £8 (near $12.50) per adult when booked in advance or £9 at the door (phone +44 0 20 7403 3761, www.tower bridge.org.uk).