Corboz‘s notion of the palimpsest immediately comes to mind when one starts to study the history of Berlin Luisenstadt and the Luisenstädtischer Kanal (Fig. 1). Now a thin strip of open space amidst the urban density of the districts Mitte and Kreuzberg, it has been a product of perpetual writing, erasure and rewriting of landscape. In the beginning, the narratives were spurred by grand urban planning visions, later by social, political and preservationist considerations. Specifically after the fall of the wall, they emerged through contention between different stakeholders [8 A range of literature was used to build an account of the canal's history First and foremost, Klaus Duntze's excellent and lively written history provided a comprehensive overview (Duntze K Der Luisenstädtische Kanal Berlin: Berlin Story, 2011) For information about city planner Peter Joseph Lenné see for example Buttlar F (Eds) Peter Joseph Lenné-Volkspark und Arkadien Berlin: Nicolai, 1989; Günther H Peter Joseph Lenné: Gärten / Parke / Landschaften Stuttgart: Deutsche Verlags-Anstalt, 1985; Schönemann H (Eds) Peter Joseph Lenné: Katalog der Zeichnungen Tübingen: Ernst Wasmuth Verlag,1993; Senatsverwaltung für Stadtentwicklung und Umweltschutz, Referat Öffentlichkeitsarbeit Gartendenkmalpflege Heft 5: Bestandskatalog der Berliner Pläne von Peter Joseph Lenné Berlin, 1990 To learn more about Erwin Barth, see Land D, Wenzel J Heimat, Natur und Weltstadt: Leben und Werk des Gartenarchitekten Erwin Barth Leipzig: Koehler & Amelang 2005 General information about Berlin's urban development and historic preservation efforts can be found in Schwenk H Berliner Stadtentwicklung von A bis Z: Kleines Handbuch zum Werden und Wachsen der deutschen Hauptstadt Berlin: Luisenstädtischer Bildungsverein eV 1998; Landesdenkmalamt Berlin (Eds) Gartenkunst Berlin- 20 Jahre Gartendenkmalpflege in der Metropole Berlin: Schelzky&Jeep 1999 2011.].

Fig. (1) Luisenstädtischer Kanal, 2014. 1 – Spree. 2 - St. Thomas. 3 - St. Michael. 4 – Engelbecken. 5 – Oranienplatz. 6 – Wassertorplatz. 7 - Landwehr-Kanal.

Fig. (2) The area (a) around 1800, undeveloped, before the extension, (b) after the construction of the canal in the 1850s, (c) after its rewriting as a succession of green spaces (1940) and (d) during the division of the city between 1961 and 1990.

Fig. (3) The hook: The original design decision idea is still visible as a succinct formal element within the urban grid of today.

Fig. (4) The development of green spaces and water features in the area from 1852 to 2013.

Fig. (5) Erwin Barth's 1929 plan to create sunken gardens is still legible today.

Fig. (6) Luisenstadt ruptured in two, 1961-1989.

Fig. (7) Development of the Wassertorplatz: On the far right, the shift towards the natural, organic design can be detected.

The historic neighborhood of Luisenstadt was one of the early and major extension in the East of Berlin‘s old inner city in the first decades of the 19th century (Fig. 2a).

Commissioned by king Friedrich Wilhelm IV, city planner and landscape architect Peter Joseph Lenné [9 Lenné was also in charge of the Berlin Tiergarten and the Gardens of Sanssouci at Potsdam Buttlar F, Eds Peter Joseph Lenné- Volkspark und Arkadien, Berlin: Nicolai, 1989 1989.] proposed a classical plan consisting of a geometrical grid of orthogonal streets for the new development at the so-called Köpenicker Feld (Fig. 2b). In order to provide access to the area, a canal was proposed to connect the River Spree in the North and the Landwehrkanal in the South. Lenné's first designs showed the canal as a straight line in the middle of an orthogonal grid.

The unusual shape the canal eventually took on – a “hook” consisting of a straight line with a quarter circle at the Northern end – originated from a sketch by Friedrich Wilhelm IV who was heavily involved in the planning process [10 Luisenstadt was named after the king's mother, Queen Luise Duntze K Der Luisenstädtische Kanal: Berlin Story 2011 2011.]. By adding the circle to the line the king already anticipated the building of the church St. Michael at the bend near the Spree. The canal was to be not merely a means of infrastructure, but also one of aesthetic experience. Built as a hook, it provided an uninterrupted view between the Landwehr-Kanal and the soon to be built church [11Duntze K. Duntze K Der Luisenstädtische Kanal: Berlin Story, 2011; p 12 . 2011.]. The visual experience of this strong axis was amplified by a number of classically designed squares, basins and a continuous row of linden trees which opened up additional vistas into the districts. Until today, the hook of the Luisenstädtischer Kanal acts a strong formal element within the Berlin cityscape (Figs. 1 and 3).

Completed in 1852, the canal proved to be vital for the transportation of building material to the area in its early years. Movement on the canal was mainly related to construction and commerce. The success, though, did not last for long. Since the slope of the canal was too little and thus the water flow too slow, the canal began to silt up. Citizens began to complain about unpleasant smells; sanitary concerns were raised. The canal came to be seen as a source for attracting mosquitos and hence a carrier of diseases. So, when in the 1920s a decision was made to build a subway connection between Kottbuser Tor and Alexanderplatz, the canal fell victim to the new infrastructural challenges. In 1928, work started to fill up the canal and turn it into a series of green spaces.

With the fate of the canal as infrastructural element sealed, the filled-up space became rewritten as an area for recreation. In 1929, horticultural director Erwin Barth proposed a sequence of gardens which were alternately geared towards leisure, horticultural education and the decorative (Fig. 4). His plan, though, was not intended to completely erase the canal‘s utilitarian past. The new areas were designed as sunken gardens 1,6 meters beneath street level, thus keeping the memory of a time alive when the green surface one was presently strolling on was made of water (Fig. 5). In addition, Barth left the basin of the Engelbecken which is situated in front of St. Michael in place and transformed it into a fish pond (or an ice rink in winter times.) Barth‘s plan was deliberately translucent to enable a reading of the canal‘s past through its present use. Though not all of his ideas were implemented, his basic approach became reality: The busy flow of commercial transport gave way to the leisurely stroll (Fig. 2c).

In 1945, at the end of WWII, the northern and western parts of the Luisenstadt were destroyed during heavy bombardment. Parts of the sunken gardens were later filled with rubble and wreckage from destroyed buildings which resulted in further eradicating the utilitarian aspect of the space‘s past. Then in 1961, the political division of the city which became established after the war was literally set in stone (Fig. 2d). The Berlin Wall was built and became the most notorious spatial expression for the political rupture marking the city of Berlin in particular and Europe as a whole. The land around the former Luisenstädtischer Kanal became part of a narrative of forced standstill and obliteration. Following the Spree from the East, the rupture line continued along the Friedrich Wilhelm’s signature loop to the Engelbecken before it proceeded further West. St. Michael was now part of East Berlin. Even today, the man-made topography of the former canal serves again as political border: It represents the administrative separation line between the districts of Mitte and Kreuzberg.

The open spaces in the Eastern and Western part of the city embarked on different trajectories. The Eastern area of the canal was completely filled-up and leveled, the linden trees were chopped down. The Engelbecken which was equally filled up with waste from nearby demolished houses became part of the border zone itself, - a sandy empty strip of land which ordinary citizens were prohibited to approach or enter. Memories of the site‘s previous lives, its infrastructural past, Lenné’s classical garden design, or Barth‘s sunken gardens, were obliterated. The sole memento left was its initial form, the hook. The site resembled a tabula rasa, but only on first glance. A new message about the unsurmountable barrier between two political systems became inscribed in space. And any attempt of rewriting it was threatened to be met with force (Fig. 6).

While the Eastern part was transformed into a lethal wasteland, the trajectory of the Western part of the Luisenstädtischer Kanal took a different turn: It became a theater for the struggle between neighborhood activists and city authorities. After years of failed top-down city planning and attempts to build a “new” city from the rubble without resident input, discontent and resistance in the neighborhoods grew. The strategies of municipal housing associations to deliberately leave apartment buildings vacant to decay led to squatting. Areas along the border strip attracted informal settlements (Wagenburgen) and alternative lifestyles. Citizens started to organize, demanding for their voices to be heard. As a remedial measure, the municipality of Kreuzberg developed special strategies for the revitalization of the Luisenstadt with a strong emphasis on public participation in the planning processes. The International Building Exhibition (IBA) 1984 became an important planning instrument during this time. One of its themes, Critical Reconstruction, focused

on the sensitive reconstruction of Kreuzberg as lively and livable neighbourhood. The impact of the bottom-up movement on design decisions for the Luisenstädtischer Kanal was considerable. Public sentiment supported approaches that broke with tradition (and thereby repudiated Germany’s recent past). Lenné’s classical concepts as well as Barth’s sunken gardens were rejected in favor of a new design philosophy featuring organic, naturally appearing forms. In architect Hinrich Baller’s redesign of the southern parts of the canal at the Wassertorplatz, the former straight lines and geometric shapes were transformed into hilly and lush park (Fig. 7). A delicate garden bridge was the only element evocative of the site’s former past.

Right after the fall of the wall in 1990, for the first time in its history as an open space, the former border zone became undefined ground. No official function was attached to it anymore, and for a short period, the wasteland developed a narrative out of its own. Its use by residents was random and temporal, governed by instantaneous needs and desires: play, strolls, or dogwalks. For a short moment in time, the ground was up in the air, with its latent possibilities in limbo.

The lack of definition invited a disparate lot of groups to stake their claims. The municipal authority for the preservation of historical gardens hoped to revive the disciplinary heritage of Lenné and Barth, while traffic planners dreamed of a new highway. In order to pre-empt the transformation of the area into a major thoroughfare, preservationists replanted Lenné‘s linden trees in 1991.

For the next decades, similar disputes were fought out by stakeholders with different agendas along different value systems and time frames. While the city’s preservationists favored a disciplinary approach and would have sacrificed some trees in order to recreate a moment in Lenné’s and Barth‘s time, a group of nature conservationists was willing to forgo preservation funds to save trees. Barth’s sunken garden had no value within their agenda; trees had. Another group feared that gentrification - now that the once marginalized district was a desirable location in the center of the city - would destroy the specific urban character of the Kreuzberg district. Their zero hour of design philosophy was set in the 80s around the struggle about Baller’s organic Wassertorplatz design when this special Kreuzberg identity came into being. Earlier memories were being ignored by this group.