If you’re travelling for work or pleasure, ask for a room on a high floor in the hotel and shoot the night skies from your hotel window. There’s always something of interest happening in the streets below even if you have a totally awful view in daytime, the nightlights can offer photographic opportunities you don’t get in the daytime.
When you’re shooting from a hotel or office window at night, turn out the room lights so you minimise the reflections in the glass. Look for interesting buildings and light effects, jam your lens up against the window and start shooting. A table or windowsill can be used to steady the camera for long exposures too.