One of my favourite look out points in Prague is at Letna Park (Letenske Sady). It’s quite a hike up to the top but it is worth the climb. The park is frequented by joggers and locals walking their dogs during the daytime but there are few people there at night and it is not that well lit. It’s a great place for taking photos of Prague’s many bridges.
I took the Metro Line B to Namesti Republicky station and took a slow walk across Stefanikuv Bridge to get there. It’s quite a long way and you might prefer to take a tram and alight after it crosses the river.
If you are visiting in summer, be sure to visit the beer garden there which is right by Letna Chateau.
Trams: No 1, 8 12 & 17