New London sits at the mouth of the Thames River on Connecticut's southeastern coast, a small city with an outsized maritime history. It was one of the busiest whaling ports in the nineteenth century and remains a working waterfront town — the US Coast Guard Academy stands on a hill overlooking the river, and the Naval Submarine Base New London is just upriver in Groton.
The Nautilus Memorial and Museum in Groton lets you tour the world's first nuclear-powered submarine, inside and out. The Coast Guard Academy campus is open to visitors and worth a walk through, and the Eagle — the Coast Guard's three-masted training barque — is often docked at the pier. Downtown New London has a handful of good restaurants and the Garde Arts Center, a beautifully restored 1920s Moorish Revival theatre. Up Huntington Street, Whale Oil Row's four identical Greek Revival mansions are a monument to the whaling wealth that once made this city prosperous. The Joshua Hempsted House, built around 1678, is one of the oldest wooden structures in New England.
Just east along the coast, Mystic has the Mystic Seaport maritime museum and a good aquarium. The Foxwoods and Mohegan Sun casinos are a short drive north if that's your thing.