Paradise found: this garden of earthly delights was one of the rare hits of the Venice Biennale.

Among the over hyped froth and flummery of this year's Venice Biennale, landscape architect Gustafson Porter's garden in the Arsenate was a rare instance of thoughtfulness that connected with more resonant forces than the curatorial flavour du jour. Despite much of the Biennale being staged in the Giardini, Venice's agreeable main public gardens, the art of landscape design and its potential for transforming both buildings and the public realm continues to be largely overlooked by curators, committees and contributors. So Aaron Betsky's commissioning of Gustafson Porter to create the first significant external landscape installation for the Biennale in its history was long overdue.

Betsky's brief drew on a phrase from Voltaire's Candide, 'il fait cultiver notre jardin', referring to how we cultivate our own garden (the French jardin secret alludes to the private part of the soul), or tend our affairs in the wider world. To achieve this requires wisdom and the desire to seek it out, yet this can often be a double-edged sword.

One of Gustafson Porter's starting points was the allegory illustrated by Tiepolo's The Scourge of the Serpents, in Venice's Accademia which employs the infamous Biblical serpent as a metaphor for voyage, discovery and self-knowledge. In the perpetual struggle between good and evil, the snake embodies both. In Towards Paradise, Gustafson Porter seek 'through allegory to tell a tale, a voyage of awareness and discovery. A voyage that seeks to question and provoke, in order that we may be able to tend our affairs.'

Perhaps more than most historic cities, Venice is plagued by a persistent melancholy, the physical relics of its past serving only to emphasise its decline as an imperial power. In their sixteenth-century pomp, the great naval yards of the Arsenale turned out a galleon a day, but are now sparsely populated by rusting vaporetti and motor boats. The sheds of the Corderie have long been abandoned by the ropemakers and now form a stage set for the follies of art and architecture.

Tucked away at the Arsenale's north-east corner, marking the point at which the docks meet the lagoon, is the site of a former Benedictine nunnery, the Convento delle Vergini, Santa Maria in Gerusalemme. Established in 1239 it was demolished nearly 600 years later in 1830 and its former precincts allowed to run wild, morphing through time and neglect into a dense, untamed thicket of brambles and ivy encrusted trees. This potent and slightly sinister locale formed the site of Gustafson Porter's allegorical voyage, made manifest through a triumvirate of garden spaces tactfully carved into the existing overgrown landscape.

The start of the journey is signposted by hexagonal sentry tower, a carious remnant of the Arsenale's original fortifications. Here, on the far edge of the former naval yard, there is a sense of stillness and abandonment, of leaving the man-made, earthly world behind. White gravel paths lead into the site, passing through the unruly tangle of planting and shaded by a stand of London plane trees. The paths wend into a rustic outhouse, its exterior densely carpeted with ivy, its chthonic interior resembling a gloomy wayside chapel. This is the Store Room, signifying Remembrance. Wails are covered in a screed of Latin bearing the names of shamefully extinct flora and fauna. Letters are starkly etched white on black and illuminated by flickering lights, like votive candles.

Studies of historical maps revealed that formal gardens and vegetable allotments were once located within the convent grounds. The second phase of the sequence. Nourishment, alludes to this narrative of organised cultivation and the abundance of the plant world which provides sustenance for both body and soul. A rectilinear layout imitates the original allotments, with rows of plants lush with fruit and vegetables inviting sampling by visitors. Simple timber benches provide points of rest and the chance to contemplate nature's riotous bounty.

The sequence culminates in a secret garden of Enlightenment, a clearing in the depths of the undergrowth connected to the other enclaves by pergola-framed paths. From the dark compression of these conduits you suddenly emerge into the light, propelled into an elongated, ovoid space with an array of gently undulating, grass-covered berms at its heart. Though intended as a tranquil place for reflection, with a sprinkling of white bean bag chairs to assist the meditative process, it also contains the most dramatic aspect of the landscape sequence.Amid the tree canopies, thin veils of white fabric languidly billow and waft in the breeze, moored in place by giant helium weather balloons. At times, these tantalising, impromptu clouds float high enough to be seen from the garden entrance, creating a sense of intrigue and drawing visitors on into the most remote part of the site.

Tensile fabric design specialists Architen Landrell helped to develop, fabricate and install the canopy and balloon structure which was erected at lightning speed in just a week. Local bylaws prohibited large-scale mechanical excavation of the site, so the shallow helical ground bankers that anchor the structure were installed by hand in the existing vegetation, causing as little disruption as possible. To minimise the visual impact of the rigging, 3mm diameter dyneema (a superstrong, lightweight, polyethylene fibre) was used, coated in a discreet, dark sheathing.

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Venice is not an obviously verdant city, but rather is full of secret gardens enclosed and hidden by high walls. Set in an out-of-the-way site, and at first inspection a sight somewhat daunting in its wildness, Towards Paradise adds to that historic continuum of secret places, slowly and sensuously unfolding to reveal a tranquil, light-filled heart. In the febrile atmosphere of the Biennale, it made for a welcome change of pace, and proved a salient reminder of the power of nature, time and place, those immemorial forces that touch and shape human existence.

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The Venice Biennale runs until 23 November www.labiennale.org