Longwood Gardens in the eastern state of Pennsylvania has been described by many visitors as a horticultural paradise and attracts hundreds of thousands of nature lovers each year.   Over the lush 424 hectares there are more than 40 different gardens and displays. VOA's Amitis Darabnia takes us inside the garden's conservatory, a large indoor facility that is home to 5,500 types of plants. Natalie Breen narrates.