If the combine really wanted to insult the resistance they would place it on the former location of he Statue of Liberty. The combine don't ever need to worry about water because of easy access to flying vehicles, but the resistance do. Then best place for NYC's citadel would probably be an island nearby to the main city. I'd imagine a lot of resistance loyal hackers would occasionally attempt to try to hack the older screens with weaker protocols to spread their own propaganda. Every monument has been torn down, and probably just replaced with a tower covered with Breencast screens and the large screens on buildings from the pre combine era that are still intact have been repurposed for breencasts and propaganda. Buildings that are close enough have those small combine walkways that connect buildings together.
The upper tier combine forces and humans don't have time for this so instead they often use drop ships to go from building to building. Most civilian and civil protection transportation is done by subway train. Due to what would've likely at the time been the largest evacuation in history the roads were more jam packed than ever, so by the time Freeman arrives the streets are still flooded with broken down cars that have been ransacked for parts or destroyed in fighting. I've sort of created a little head cannon about what New York City was like.
