In Portsmouth, England, the Spinnaker Tower (Gunwharf Quays, Portsmouth, Hampshire, PO1 3TT, U.K.; phone +44 0 23 9285 7520), a 557-foot-tall observation tower, offers 360-degree views, including Portsmouth Harbor, the coast and the Isle of Wight.
There’s a glass floor on View Deck 1 and a café on View Deck 2, with Deck 3 open to the elements. Open 10 a.m.-6 p.m. Admission, £8.25 ($13). 15% discount when booked on website. Family tickets (2+2) at www.great2012offers.com.