Use article the or no article. clyde, blackpoll, ontario, severn, mississippi, andes, snow don, ireland, wales, trafalgar square, sevan, ben nevis, liverpool, hyde park, canada, fleet street, central park, oxford street.

the Clyde (river), Blackpoll, Ontario, the Severn, the Mississippi, the Andes, Snowdon, Ireland, Wales, Trafalgar Square, the Sevan, Ben Nevis, Liverpool, Hyde Park, Canada, Fleet Street, Central Park, Oxford street.