There other places in town with magnificent vistas over Berlin (Siegessäule, Potsdamer Platz), but usually you have to pay. The Viktoriapark is entirely free, and can be found in one of the nicer neighborhoods of Berlin: the one around Mehringdamm.
The hill (wouldn’t dare to call it a mountain) is dominated by a large monument. From there, a waterfall runs straight down. Close to the top is a kiosk as well for the required refreshments when you walk up.