This year's German garden festival is at Potsdam, long associated with pleasure and with gardens. Its ruling family, the Hohenzollerns, despised Berlin and its irreverent citizens and thought Potsdam, with its lakes and bucolic landscapes, to be a far more civilised alternative for their court.
Prominent architects and landscape designers were employed to create a suitable backdrop for the court's activities, leaving Potsdam with superb Baroque buildings and Peter Joseph Lenne's glorious parkland, laid out in the English style and taking full advantage of the woods, rivers, lakes and farmland of what was known as Potsdam Island.
But both world wars changed that. In the first, Potsdam lost its primary role as a royal residence when the Kaiser abdicated, while the second caused huge physical damage - chiefly because of the city's proximity to Berlin. The subsequent Cold War did little for Potsdam's status, leaving it stranded in the communist east; and what the RAF started, the communists finished, with large-scale clearance of much historic fabric that remained.
The rather confused juxtaposition of old and new in Potsdam is evidence of largely botched attempts by post-war planners to create a 'new socialist Potsdam', unencumbered by its imperialist past. But many beautiful buildings, including the main Schloss in the centre, were needlessly demolished, and the city's connections with the surrounding landscape were severed.
Instead of a royal garrison, Potsdam became a Russian one.
Nonetheless, with reunification Potsdam once more could connect with the larger Germany and, by the mid '90s, was planning to reverse its previous decline by bidding to host the 2001 Bundesgartenschau (BGS) or Federal Horticultural Show, which would be celebrating its 50th anniversary.
Rather misleadingly named, the BGSs serve as large-scale landscape and openspace planning exercises, far beyond the confines of a garden show, and their legacies have been of great credit to several German cities. The shows attract a great deal of funding and sponsorship which boosts the local economy, and Potsdam is no exception. An overall budget of more than £100 million (one-third of which came from the state) allowed the city to set its sights high.
With an inappropriately modest theme of 'The Art of Gardening - Yesterday, Today and Tomorrow', Potsdam broke the mould of previous shows and decentralised the exhibition, with three other venues in addition to the main grounds, each with their own agenda. This was a challenge to achieve, as the German horticultural industry sees these festivals as its showcase and feared that a dispersed exploration of urban design would be bad for business.
But the private company created to organise the BGS from 1995 pushed through its radical policy, producing a fascinating result that re-examines the whole philosophy behind such exhibitions.
Certainly this BGS exploits existing assets more than some of its predecessors and, by connecting well known parks and spaces throughout Potsdam, it has presented in effect more than 300 years of landscape history and design.
The main venue is the 73ha BUGA-Park at the Bornstedt Field on the city's northeast edge; but next to it is the Meadowland, an impressive agricultural expanse, which probably evokes the historic and cultural links to its surroundings, traditionally enjoyed by Potsdam, more than any other element of the BGS.
Although superficially natural in appearance, this carefully composed landscape was created by Lenne in the 19th century as a 'feast for the eyes' which depicts the interaction between man and animal. In keeping with the original historic intent, the BGS has incorporated examples of varying cultivation techniques espousing the values of 'greenness', while showing how the Kleingartens (allotments) so beloved by German townies can be managed responsibly.
The second and much more dispersed theme of the BGS is found in several interventions in the historic city centre, which are the moves at greatest variance from previous shows. Among them, the old Lustgarten associated with the vanished Schloss is being recreated with new plazas, formal gardens and restored historic archways. Unfortunately, a lot of this work is still going on, which is bad timing, but even now the difference to Potsdam's urban fabric is marked.
More impressive is the revised Reunification Square, a striking geometric design of tilted lawns and stone steps that offers superb views to the Nikolaikirche, Potsdam's symbol. In addition, many of the traditional Innenhoefe (courtyards) are being restored, and a portion of the city's canal that was filled in during the '60s is being restored. All these interventions should revitalise the town's relationship with the Havel river.
Also linked to the river is the third theme area, the Riverside Locations (Orte und Fluss), aimed at reversing the decline of these significant riparian parks. New paths and ferry points will again connect Potsdam to Babelsberg's parks and palaces to the north. Particularly impressive is the newly created Nuthepark at the rivers' confluence, with new bridges and footways to adjacent residences.
Similarly, the north bank has been restored, promoting connections from the Havel to the old market square, the Rathaus and the theatre. The centrepiece of this area is Freundschaftsinsel (Friendship Island), which has been overhauled to create a series of interconnected gardens based on the historic '30s designs of Karl Foerster, one of Europe's greatest plantsmen.
These charming spaces overflow with the delicate and subtle plant arrangements that distinguishes Foerster's work. Elegant pergolas, hedges, linear pools and colourful perennials create some beautiful vistas and alert the visitor to Potsdam's ubiquitous rivers. These public gardens, a reminder of Germany's rich landscape traditions, are executed to such a high standard that they are sure to become one of Potsdam's most popular open spaces.
The main focus of the BGS is the Bornstedt Field: formerly a Soviet military training ground, its landscape was scarred and derelict, with scattered remnants of woods, meadows and agricultural land. The design has attempted to enhance these landscape types as much as possible while providing a pattern of gardens and elements to unify the park.
This has only been a qualified success - often the relationship between the constituent parts is disjointed. There are few large-scale gestures, such as avenues or lakes and streams, to bring a rigour into the spatial arrangement.This rather laid-back approach to the layout is at odds with Potsdam's landscape tradition but is in keeping with the economy of the BGS's approach. The cost of the cityscape improvements has inevitably meant the curtailment of major landscape interventions at the BUGA-Park.
Some of this has been beneficial: the seemingly obligatory monorail has been dropped, for example, and in the long run not having some of the more expensive temporary elements is no bad thing. Moreover, the ephemeral treatment of much of the exhibition's periphery is because an unusually high proportion of the Bornstedt Field will in time be devoted to recreation and housing - a new community with its own green lung.
This is not to say that Potsdam is bereft of interesting landscape design.The centre of the site is dominated by an adventurous assembly of sculptural angled and lawned walls of earth, interconnected by ramps and bridges. These striking elements act as lookouts, giving a changing and dramatic aspect to the gardens and their water features, but also create acoustically improved performance spaces.
The scale of the sculptures is impressive, and the result is all the more admirable when you realise how many of the old military structures have been absorbed into the resultant bold green slopes.
The strong geometry and idea of 'stacking landscape' are continuing themes in the Biosphere exhibition hall which dominates the BUGA-Park. Designed by Berlin architect Barkow and Leibinger, this concrete structure provides nearly 4,000m 2of exhibition space.
Arranged as a series of faceted landscapes (stone, timber logs, slate), with an artificial plain of green lawn for a roof, this structure borrows its aesthetics from the neighbouring ramparts and creates spaces which blur the distinction between built form and landscape. A striking water rill bisects the building, and the plaza at its entrance is graced by a grove of honey locust trees.
Other impressive features include a water playground, with huge stainless-steel fish fountains and swing bridges that will no doubt prove immensely popular during the summer (a franchise for loaning towels here would make a fortune).
Many of the gardens displayed a clever balance between art and education: in honour of the BGS's anniversary, for example, a set of gardens from the '50s to the present day is a reminder of how fashions have changed and how awful some ideas were.
Some gardens reflect changes in maintenance techniques and recycling (a popular topic in Germany); others are carefully arranged within areas of retained woodland, showing just what will work in demanding places. There are green classrooms which can be rented by local schools; a surreal arrangement of massive tilted stone pyramids, each accommodating radically different plants, which was rather like walking through an Escher print; not to mention a 'plant bar', with plant arrangements representing cocktail drinks.
The usual displays (roses, perennials, orchards, allotments) were also present, but more significantly the site's neglected meadows and fragments of woodland have been responsibly restored, with subtle interventions that minimise the impact on sensitive habitats but at the same time provide facilities for education.
Overall, the BUGA-Park connects seamlessly with the city and is readily accessible by foot, cycle and an improved public transport system. The particularly impressive aspect of this year's BGS, though, has been its audacious re-examination of what these events should provide.
The festival has done more than create a new park for posterity - it has taken stock of what parks and open spaces are for and realised that their interconnectivity is vital to the life of a city. Its restraint has produced some visitor disappointment, with claims that the other improvements should be happening anyway, and not under the banner of a garden festival. But that is to ignore the huge positive changes in perception that accrue from these events.
Bearing in mind the enormous cultural and historic value of Potsdam's elegant landscapes, to have produced a stand-alone new park full of temporary gimmicks with no contextual references would have been short-sighted - it is just surprising how committed Potsdam has been to another way. I am sure its far-sightedness will be validated.
Peter Sheard is a landscape architect with Gensler in London