Or perhaps it was a combination of your mood that day and the ambience of the gardens through its landscape design. There is a lot of research being done on green spaces and the different impacts they can have on psychology and moods. I think that the ancient classical civilizations of Southern Europe like the Hellenistic cultures of Greece and the Etruscans and Romans of Italy grasped the wisdom of cultivating sacred groves and gardens and realized that these were inherently good for the soul.
Its interesting that you mention the turtles because the presence of animals either wild or captive in botanical gardens is something that I find decisive on whether I enjoy a visit. I guess its something related to the Biophilia hypothesis but apart from feeling immersed in floral surroundings the presence of fauna just adds to that overall feeling of connection. For example , whenever I visit Kew Gardens I love to watch the antics of the Chinese waterdragons that are kept in the waterlilly house , in the UNAM gardens in Mexico city its the hummingbirds and butterflies while in the Sao Paulo botanical garden in Brazil I really enjoy watching the wildlife , the sloths , toucans and monkeys.
On the subject of Italian botanical gardens , I am really hoping to visit Italy in the New Year and was wondering whether you have visited Lazio or have any further reccomendations ?