The Masnedsund Bridge connects the southern tip of Zealand to the small island of Masnedø, and from it you get clear views across the Storstrøm strait — the body of water that Vordingborg Castle was originally built to control. The older Storstrøm Bridge, a slender railway structure from 1937 that runs parallel to the newer road crossing, is particularly photogenic.
The area around the bridge has a few walking paths and is a reasonable spot for birdwatching in migration season — the narrows funnel birds coming south from the rest of Zealand. The island of Masnedø itself is quiet and residential; there is little reason to cross unless you are cycling the South Zealand coastal route.