Tacoma Narrows Bridge and back. It was noisy but a good workout -- about a mile each way on the bridge itself, plus some meandering through a park and a doughnut shop on the other side.
History buffs may remember this bridge as "Galloping Gertie," which opened in July 1940 and collapsed four months later due to a physical phenomenon called "aeroelastic flutter." This earned the bridge a place in many physics books. It got its nickname before the collapse because construction workers noticed vertical movement of the deck during windy conditions. The replacement bridge built in 1950 now accommodates westbound traffic. A second span, opened in 2007, handles eastbound traffic.
(As always, if any of you eagle-eye readers find errors, please correct me.)
Have a colorful day!