When visiting the Longwood Gardens, I highly recommend spending time at the Main Conservatory. At this time of the year, apart from all the different varieties of flowers on exhibit, they also have pools filled with more than 100 types of day and night-blooming tropical waterlilies, hardy waterlilies, lotuses, giant water-platters and other aquatic and bog plants.
Giant platters or pizza.
I spent hours sitting and just watching these water lilies. They're so beautiful most especially when you discover the ones that bloom at night.