It's Valentine's Day. How will you show your special one the depth of your love? If you're near Philadelphia and appreciate a hyper-literal interpretation of symbolism, we suggest taking a journey into a human heart. The Franklin Institute's Giant Walk-Through Heart provides visitors with an inside look at the "engine of life," with narrow passages that follow the flow of blood through veins, arteries, valves, and chambers to the ever-present cadence of a heartbeat. ]]>