This East Dorset resort town in the United Kingdom features boatloads of family fun, with a water park, large beaches and several appealing museums. The harbor itself is gorgeous; it's one of the biggest natural harbors on earth. Poole cruises dock in the city's South Quay terminal.
Head to Hartland Moor National Nature Reserve, a protected area outside of Poole that hosts an array of indigenous animals in its misty bogs -- it's well worth a day trip. The reserve is also home to the spectacular ruins of Corfe Castle, more than a thousand years old.