I have a little travel tripod about six inches long that comes in handy for shooting dark indoor spaces or outside at night. Here's the interior of St. Patrick's Cathedral. This is a 15-second exposure, which is why the people in the aisle look like mist. (Click on images for larger versions.)

Here's another attempt at a Grand Central Station blur. I didn't want everyone to be mist, so this is a shorter time exposure of 1.6 seconds.

There are some rose sculptures on Park Avenue. I tried some time exposures but it turned out that just using flash worked best.