Hammacher strives for as complete an overview as possible of sculptural art ‘from Rodin to the present’, on the same level as the painting collection and that ‘follows the same line of development that Mrs Kröller indicated in her collection’. He has to make tough choices, ‘but a basis, a core, must be there, if one is to see out of which main elements the new sculpture has developed. That is why the acquisitions are now focused on the old masters of modern sculpture, but at the same time on the younger generations’. In a short period, Hammacher acquires Angel torso from 1925 by Jacob Epstein, as well as Large figure from 1958 by Joannis Avramidis, Composition by Otto Freundlich, cast from a plaster model from 1933, and Remake of idea no. 3 from 1957 by Edgardo Mannucci.

In 1961, specifically for the sculpture garden, Hammacher acquires the bronze sculpture Cloud shepherd by Jean Arp, a smaller version of the three-metre tall plaster sculpture that he saw in 1954 at the exhibition Sept pionniers de la sculpture in the Swiss town of Yverdon. He writes to Hepworth that the work makes an extra-terrestrial impression on him, ‘like something fallen from the moon’.

Thanks to the acquisitions in 1960, English sculpture is well represented in the collection. But still high on Hammacher’s wish list is the work of Henry Moore, whom he met in New York in 1953: ‘He is essential in a basic collection, but the difficulty is to acquire an important work’. The idea of a sculpture garden appeals to Moore and when the plans become more concrete as of 1957, he visits the museum every year. He is happy to help think about a suitable sculpture and suggests an early work, while Hammacher would rather that he makes a work especially for Otterlo. In the end, the London art dealer Harry Fisher successfully proposes Two-piece reclining figure II from 1960, which the artist describes as ‘the fusion of human and landscape forms’. Fisher: ‘Moore says that this is his best work […]. It is the culmination of his life’s work.’

The colossal sculpture arrives in Otterlo in the first week of May. On Moore’s advice, Hammacher places the work on top of a tree-covered dune and writes to him after the installation: ‘I think it is quite good to discover this marvellous sculpture suddenly there’. The artist makes a bronze cover plate for the pedestal and several trees are felled at Fisher’s request: ‘I am so happy that you […] agree that Moore’s sculpture should have a little more air and that the trees should be cut so that it can be seen when entering the garden.’ Moore’s wall sculpture Animal head is also acquired this year and it too is placed in the sculpture garden.

Hammacher meets the Hungarian artist Marta Pan in 1959 at a CIAM conference that is held at the Rijksmuseum Kröller-Müller, where she accompanies her husband, the architect André Wogenscky. Two months later he visits her studio in Saint Rémy. Her oeuvre is still relatively small, but Hammacher is impressed. He gives Pan her first official commission: a sculpture for the sculpture garden. He gives the same commission to Hans Aeschbacher after visiting his studio in Zurich.

Hammacher invites both artists to Otterlo in order to ‘allow the terrain and its possibilities to sink in’, to discuss this and then to develop a concept. The positioning of the eventual sculpture is also part of this process, as he later writes the idea is: ‘not only to have the sculpture as an object, but for it to incorporate the entire ground plan and the situation of the museum building. Hence the conception of the intended sculptures has occurred in a landscape-architectural connection’.

Aeschbacher produces his three-metre tall granite Large figure I in a marble quarry near Bellinzona and transports it to the museum on 4 May. He stays in Otterlo for several days for the placement. He has carefully calculated where the sculpture must be placed and works on site to finish the concrete base plate.

Pan designs a floating sculpture and a large pear-shaped pond as a ‘carrier’ for the sculpture. Hammacher fully supports her plan, but Bijhouwer finds a pond on the sandy Veluwe ‘unnatural’. Eventually he agrees to a smaller pond, so on 23 May 1961, only a week before the official opening of the sculpture garden, Floating sculpture, Otterlo can be launched. Pan had been working for six months on a wooden model that became the basis for the final polyester sculpture, ‘an ideal material for a floating sculpture’.

The close collaboration with Moore, Aeschbacher and Pan is also special because Hammacher does not invite any of the other artists to be present during the placement of their work. He develops a good relationship with many of them but keeps the installation of the sculpture garden for himself.

Hammacher places over 40 sculptures in the sculpture garden, on carefully designed brick pedestals that are smoothed over with cement or covered with grass. Some works, such as those of Rodin and Epstein, are placed on a block of Maulbronn sandstone. Bijhouwer is impressed by the ‘virtuosity’ with which he makes use of the variations in the landscape in combination with the materials used.

On the lawns, Hammacher makes spacious arrangements of groups of sculptures in which one masterpiece is central. For example, Lipchitz’s Song of the vowels, Bourdelle’s Pénélope and Martini’s Judith and Holofernes play a leading role amidst the work of lesser-known sculptors. As in the rooms in the museum, a specific theme or style is represented on each lawn. To the left and right of the most northerly path, Hammacher places only abstract sculptures, but he also creates a lawn on which the human form is central. A number of works have been loaned for the occasion. Hammacher wants to thereby draw the attention of the Advisory Committee to certain shortfalls in the collection.

He reserves the first field, the closest to the museum, for Pan’s Floating sculpture, Otterlo, Aeschbacher’s Large figure I, Hepworth’s Figure (Archaean) and Arp’s Cloud shepherd. These sculptures demonstrate a variety of techniques and materials and form a visual introduction to the rest of the sculpture garden. The main focus is on modern sculpture, but the work of the ‘great predecessors from the 19^th century, such as Rodin, Bourdelle and others’ will also form ‘a small, carefully selected basic collection’. This approach ensures that the sculpture collection in the garden ‘will show a new informative facet of the path of history […] according to the pattern that Mrs Kröller herself indicated’.

The sculpture garden is festively opened on 3 June 1961 in the presence of an international group of artists, critics, curators and museum directors. Hammacher describes the garden in his impassioned welcome speech as an ‘alphabet of spatial forms’ in which the observer can find depth and enrichment by regarding the sculptures as ‘symbols of life’.

As a member of the Advisory Committee, the sculptor Oswald Wenckebach wants to make a contribution and devises an entertaining opening ceremony. He makes a relief as large as a door with an abstract polystyrene representation of a mammoth. The Minister of Education, Arts and Sciences, Jo Cals, who would introduce the Mammoth Act two years later, has to break through the polystyrene to be the first to enter the sculpture garden. Then the guests are given a tour of the garden. The reactions are complimentary.

Hammacher also continues to focus on the painting collection. In 1961 he acquires a pastel drawing by Odilon Redon from the former collection of H.P. Bremmer. He calls Marie Botkine in an astrakhan coat ‘a particularly striking ladies portrait’.

A retrospective of the work of James Ensor, from the collections of museums in Brussels and Antwerp and from private collections, opens on 17 June. This is ‘amazingly enough’, according to Hammacher, ‘the first time that such a retrospective of the work of this great Belgian painter has been shown in the Netherlands’.