On the map in the lower left corner you can find a yellow stick figure. When you hold the left mouse button on it, a blue line will appear in the map in the area of roads. This blue line tells you where you have to drag the stick figure and then release the mouse button. Once you do so, you will reach "street view" map mode through which you can observe the entire area of Lednice-Valtice, as if you were actually on the spot.
If you wish to exit “street-view” map mode, just click on the arrow in the upper left corner of the map.