The most curious thing about this picture is not the tall plant with the big leaves in the middle, or the two pairs of men working in the field either side of the plant, not even the large white long-fingered shape in the lower right-hand corner of the image. Not even the title of the book, visible in the banner in the sky, Rabarbarologia Curiosa, is strange. The strangest thing about the image is, in fact, the architecture of the city in the right-hand background of the image:
A close look at the city reveals white-washed walls with small openings surrounding a city with several tall buildings, a round tower on the far left of the city walls, an entrance gate with what looks like battlements, and near the far right of the walls of the picture a wide flat-fronted building with a decorative façade. On top of the hills in the background stand several other buildings, one church-like with a tower but no spire, the other with a gable and a spire but no tower.
To understand why the architecture of this city is the most unusual thing about the image, we have to begin by making sense of all the other things: the title of the book for which this serves as the frontispiece, the plant in the middle, the working pairs either side of the plant, and the white long-fingered shape in the front right-hand corner.
The full title of the book is rather long – see below – but the short title is Rhabarbarologia seu Curiosa Rhabarbari Disquisitio, which translates as ‘The Study of Rhubarb’ or ‘Inquiry into the curious rhubarb’ 
In 1679, when this book was published, scholars, botanists, physicians and travellers had been writing about the rhubarb root and its remote source for many centuries. One of the first Europeans to write about rhubarb was the first-century Greek physician Dioscorides, who described the medicinal qualities of the root of rhubarb, which could have a settling effect on an upset stomach.
The illustration to the right is rhubarb root, from a sixth-century manuscript known as the Vienna Dioscorides, or the Juliana Anicia Codex, 284v.
Marco Polo came across rhubarb in several places in China in the thirteenth century; fifteenth-century Dutch recipies talk of ‘rebaerbe, soffraen, ende ghaligaen’ (rhubarb, saffron, and galangal); and in the sixteenth century, rhubarb was used as one of the prophylactics used against the Pestilence, as we see in this page of Paracelsus’ Für Pestilentz [Against the Pest], where he recommends a stringent programme of blood-letting, and taking rhubarb pills and powders. 
In the second half of the seventeenth century, when Mathias Tiling (or Matthias Tilingius, as he was known by his Latinized name; 1634-1685) published this study of rhubarb, the knowledge about rhubarb in Europe had been transformed. Jesuits and other travellers had begun to frequent China, bringing back first-hand observations about the cultivation and storage of the rhubarb plant.
The Polish Jesuit Michal Boim, who was in China from 1643 to 1659, published Flora sinensis in 1656, with this beautiful illustration of rhubarb.
In Europe, the second half of the seventeenth century, then, was a time of growing knowledge of botanics and materia medica. Richly illustrated books appeared, which included detailed drawings of the varieties of the rhubarb plant and its root. Tiling’s book includes not only the drawing of the plant in the frontispiece, with its big leaves and the root next to it, but also several illustrations inside the book, including one with the different varieties of the rhubarb plant growing in Europe ; and another page with the so-called ‘true rhubarb’ that was thought to have come from China: rhabarbarum verum ; and finally the famous root that was so desirable for its purgative qualities: rhabarbari Radix :
The representation of the root here is quite different from the root in the frontispiece, but that is explained by the word frustum, ‘a piece’ or frustillum, a ‘small piece’. The root was harvested with its various tentacles or ‘fingers’ attached, but by the time the root arrived in its desiccated form in Europe, it had been reduced to pieces or even small pieces.
The Dutch visitor to China, Johan Nieuhof, had added in his 1669 ‘An Embassy from the East-India Company of the United Provinces, to the Grand Tartar Cham Emperor of China’ that rhubarb ‘doth not grow wild, as some report, but is rais’d and increas’d with great care and diligence.’ The idea of rhubarb as a crop that was raised and increased was entirely new to the European observers. In Tiling’s illustration we see evidence of this knowledge in the figures to the left and right of the central plant.
All this should make clear why the subject of this book, the plant in the frontispiece, and the representation of the plant in the middle, the working pairs either side of the plant, and the white long-fingered shape in the front right-hand corner are not very surprising at all.
So why is the city in the background strange? Probably because at this point, in the second half of the seventeenth century, both knowledge about rhubarb coming from China, and visual representations of the Chinese landscape were circulating more extensively throughout Europe than ever before. And although much of Chinese landscape was shaped more by the imagination than by first-hand accounts of the countryside, certain conventions had emerged. No one had contributed more to these conventions than the publishers of Johan Nieuhof’s work. Arguably, the illustrations from Johan Nieuhof’s book had started to set the standard for what China looked like in the European mind’s eye. This fortified city, with its white-washed walls, small windows and church-like buildings, and its entrance gate with battlements, looks perhaps North African or Middle Eastern, but certainly nothing like the cities in Nieuhof. And that, perhaps, is the most curious thing about this scholarly book devoted to the rhubarb root.
 Matthias Tiling and Mouton-Fontenille de la Clotte, Matthiae Tilingii,… Rhabarbarologia seu Curiosa rhabarbari disquisitio, illius etymologiam, differentiam, locum natalem, formam… atque usum pharmaceuticum, chymicomedicum, omnibus pene humani corporis partibus destinatum, additis diversis observationibus & quaestionibus rhabarbarum concernentibus, detegens… (sumptibus Jacobi Gothofredi Seyleri, 1679).
 Paracelsus, Für Pestilentz Ajn seer nützlicher vnnd bewerter Tractat, der Christlichen gemayn zu nutz vnd wolfart ([S.l.], 1554).