Neighborhoods

A Neighborhood is a 4 x 4 x 4 crewable decor that allows you to keep many houses in a small amount of space in your empire.  It's item code is BB24.

A Neighborhood can hold up to 3 blocks (levels or floors).  The image shows a block holding 9 houses, but this seems to be incorrect.  According to Zynga's official announcement, a block holds up to 5 houses.  Thus, a fully built Neighborhood would be able to hold a total of 15 houses in the flat space of 4 houses (4 x 4 cells).

You expand a neighborhood by building new blocks on it.  To do so, you must collect parts from neighbors.  For now, you can only build one Neighborhood.  External housing bonuses do not apply to Neighborhoods.

Quotes from the game:

• When you can't expand outwards, go upwards. Put Houses together in a high-rise Neighborhood to take care of some of your real estate issues!
• Build the Neighborhood to clump Houses together and save on space in your Empire.
• Add Houses to your Neighborhood to save on housing space in your Empire.
• Expand your Neighborhood to get extra Coin payouts.
• Note: You can harvest the Houses whenever they're ready with just one click.
• 5% Coin bonus in Block 1; 7% Coin bonus in Block 2; 10% Coin bonus in Block 3
• Do you want to harvest the Houses in your Neighborhood for {total} Energy?

Here's a very large picture of a 3-block neighborhood where you can see the individual houses in it: