The garden is an island, separated from the mainland, in order to emphasize a distinct order of being- the intelligible order. The entire island is a garden, governed by Venus, and so everything here is dedicated to beauty.
The Renaissance philosopher Marsilio Ficino wrote of two Venuses: one is the earthly goddess whose temple the lovers have visited on the far shore, and the other is this celestial Venus whom they will ultimately catch a glimpse of as she bathes in her fountain at the centre of the amphitheatre.