With Googlemap you get live view of the fortress grounds. You expand / reduce the map by scrolling with the mouse pointer over the map. Or use your thumb and forefinger if you use your mobile phone.
When you click on the red dots a box with text / images opens up. Click the X in the upper right corner to close the box.
The red dots turn white when you click on them. It helps you keep track of which points you looked at.
To get to the map, click on the text To map at the bottom of the screen.