Duplicate your picture of New York (CTRL - D)
In the new picture you created, crop the image to the area that you want to
feature (use the Crop Tool on the Picture Tool Bar. The tool bar becomes
visable when you click on the new picture. If not, go to View > Toolbars and
make sure the Picture tool bar is checked).
After you've cropped the new image hold the enlarge it proportionately.
If you're using PPT 2002/2003 you can animate the new image with the Faded
Zoom effect (Slide Show > Custom Animation > Add Effect > Entrance > Faded
Zoom. Adjust settings as desired.
Repeat above for second image.
Another feature that will add pop to your new images is to place a nice soft
shadow behind them. You can download a free trial version of PPXSoftShadow -
a PPT add-in. It's inexpensive to purchase and easy to use.
Let me know how this works for you.