Sky-high sand dunes and excellent waves for surfing.. In Short If you think a beach isn't really a beach unless it's got serious dunes, Marconi is for you. Dunes are so high here they block the afternoon sun. Surfing is allowed away from the guarded swim area. The beach is part of the Cape Cod National Seashore. If you want to see the shore from a different perspective, head to the lookout platform at Marconi Station--it has 360-degree views of the Atlantic and Cape Cod Bay.