This site gives you the distance and directions of nearby towers as well as advice on what antenna might be best for you, based on your home address. (nabpilot.org)
These can be spent on one of two upgrade towers, which don't attack enemies but boost either the damage or range of nearby towers. (playstationlifestyle.net)
Completing the picture were the colossal 11.5 - metre - tall Olympic rings suspended from nearby Tower Bridge. (canadianbusiness.com)