Floods swept through eastern Germany and the Czech Republic in August 2000. In the beautiful city of Dresden, the River Elbe burst its banks, turning the city into a lake. The vaults of the Zwinger Palace which houses Dresden's art treasures were flooded, and only a huge rescue operation saved more than 4,000 works of art. The Royal Academy of Arts is holding an exhibition of more than 50 paintings from this famous collection, to remind people that Dresden has now returned to normal and can once again be visited. The exhibition, Masterpieces from Dresden, Mantegna and Duerer to Rubens and Canaletto, celebrates a remarkable collection, founded in the early 1700s by Augustus the Strong, Elector of Saxony and King of Poland, and greatly extended by his knowledgeable and cultivated son, Augustus III.
The exhibition, which runs until June 8, includes paintings by Duerer, Mantegna, Titian, Ribera, Murillo, Vel zquez, Canaletto, Bellotto, Poussin, Watteau, Rubens, Friedrich and many others. There are portraits, cityscapes and landscapes, paintings from ordinary life, mythology and the Bible.
This view of the moat of the Zwinger in Dresden is one of five large paintings by Bernardo Bellotto, who painted 14 views of Dresden when he was court painter to Augustus III in the mid-1700s. The word Zwinger means "the area between outer and inner defence walls", which is where Augustus the Strong built the palace as a festival building, about 20 years before Bellotto painted this view. It is this building that houses the Dresden collection itself.
Bellotto took his view from the greenhouses of the Orangery. You can see the columns of the palace courtyard and its gold-topped dome on the left of the canal, in front of the wooden bridge. Just to the right of the canal, in the background, is the squat, red-roofed tower hiding the water tank for the Zwinger fountains. The half-timbered building on the right is the scenery workshop for the opera house, the large building behind the Zwinger with two church towers rising above its roof.
Although these are prominent buildings, their role in the painting is not as important as you might think. Columns and windows merge together to form a detailed patterned horizon that curves round the main subject, the moat and its banks. Measurements would show that most of this composition is made up of air, stone, water and leaves. On the right bank of the canal, we see people strolling, chatting and courting among strictly pruned trees, while on the left bank, within the Zwinger, more aristocratic-looking people greet each other and flirt among more natural-looking trees. These trees, the domes on the buildings, and the swans' necks provide some of the very few curves in a picture otherwise composed of verticals, diagonals and horizontals. This geometry gives a solid setting through which the changing water of the moat can flow.
We experience much of the painting through contrasting textures: the rough stones of the moat wall in the heat of the sun; their coolness in the shadow; the cold wetness of the skin of the water; the sharp corner of the moat wall; the soft bushiness of the trees and grass; the cool air all around. We can imagine sounds: the distant rumble of the carriage crossing the wooden bridge; the swish of the swans in the water; the murmur of people's voices. Such movement is slow: swans glide; people stroll under the trees; the shadow shifts along the wall; clouds float aloft. We are invited to contemplation.
If you could look even more closely at the surface of the water, and at how it is painted, you would see broad transparent brown brush marks on the ground of the canvas, which is painted beige. Over these rough marks, there are fine, opaque strokes of soft grey or brown, applied with a sable brush: vertical for the reflections of the canal wall and the buildings, and horizontal for the marks made by the breeze as it ruffles the water. The reflection on the surface prevents you seeing the water's depth. But the vertical marks of the reflections suggest depth while the horizontal marks suggest surface. This water is rather like a commentary on painting, which is literally all on the surface, but suggests depth. Many things in the picture are half-hidden: the buildings by other buildings and trees, and also by the fact that they are shown only from the side and not from the front. People are half-hidden by trees; the depth of the water by reflections; the foreground by deep shadow.
You could stay here for hours, thinking about the scene, as if you were actually there and, at the same time, thinking about how paint conveys the scene. Bellotto has caught a moment and kept it for the future. He turned paint into walls, water and clouds and made decisions that a camera can never make. However, it is thought that he did make use of a camera obscura, as perhaps did his uncle, Canaletto, and many other painters of his period. This he would have used as a tool with which to lay out the drawing and perhaps to judge the tones of the scene in front of him, but we don't know enough about how artists used these devices, or even for sure if they did. As with magicians, artists don't like to give away their tricks.
What we do know from his paintings is that Bellotto was a master of realism, who also enjoyed showing us the people of the city from all walks of life and even those visiting from the surrounding countryside, in the foregrounds of his paintings. Sometimes, for example, we can see washing out on the line, and daily life going on before us with the city as a backdrop. These foregrounds are often in deep shadow.
If you do have the chance to visit the exhibition and to look at the other Bellotto paintings on view there, you will see what a fascinating series of portraits he gives us of Dresden as it was in the mid-18th century.
Anne Harris is deputy head of education at the Royal Academy.
Key stages 1 and 2Collaged reflections: explore how transparent colours change the look of underlying colours.
* Using sheets of paper of different colours, fold each sheet in half and draw houses on both sides, with the bottom of each house on the fold.
* Unfold the sheets and stick them in a line in the middle of a sheet of beige paper, so that the bottom halves look like upside-down houses.
* Stick blue cellophane over the upside-down houses - this is your river.
* Stick blue and pink ripple-shaped cellophane over the blue cellophane water.
* How has the transparent blue changed the colour of each house?
* Draw people walking in front of the houses, and other objects, such as clouds and trees, and make their reflections in the river.
Transparent paint: explore colour by putting transparent paint colours over the top of dry paint so that the bottom colour shows through.
* Research and make your own camera obscura. You could use a shoe box and you will need a lens.
* Choose a section of textured wall of stone, brick or plaster and make a small painted study of this section, concentrating on texture and making it look as real as possible. Try doing the same thing with other surfaces, such as water and reflections, and grass.
* Collect textures, including postcards or reproductions of paintings that show an interest in texture, such as the Welsh painter Thomas Jones's paintings of Naples buildings or paintings by Frank Auerbach, where the painting itself is textured.
Create a collage of a city scene with this collection.