Building a Lego city is a great way to enjoy your entire Lego collection all at once. Children love it. It doesn't matter if your Lego sets are in different scales or from different time periods. Getting all your Lego sets together in a Lego city entices the imagination and encourages the creation of new Lego structures.
Clear a big, open space. A Lego city requires a lot of room. A very large table or clearing on the floor works nicely. Just be sure that no one will need that space for a few days. Considering how much work it takes to create a Lego city, it would be a shame to have to tear it down right away.
Lay out your Lego mass transit first. If you have a Lego train set, make a track that goes around your Lego city. This will provide a basic outline. The other amenities of your Lego city will grow around your mass transit.
Create infrastructure. Use your spare Lego blocks to create some tall buildings and maybe a monorail. It is nice to make your monorail to go through some buildings. The idea is to give your Lego city a skyline.
Build all your Lego sets. These include buildings, vehicles, spaceships and whatever else you have. These will become the building blocks of your Lego city. Make a Main Street in between the buildings. Line the businesses up and create a road through the middle of town.
Let your Lego vehicles hit the road. Get them all out. It doesn't matter if they are race cars, ambulances, police cruisers, fire engines, monster trucks or cranes. All vehicles are welcome in the Lego city. Arrange them logically. The ambulances should go near the hospital, the police cruisers near the police station, and so on.
Erect some Lego parks and green spaces. Even Lego people need parks. Gather your Lego trees, grass and benches and create some green space. Place them around your Lego city to break up all the urban monotony.
Put your Outer Space Legos up on the Moon. You can create a separate Lego world full of spacecraft and put them on a chair or ottoman next to the rest of your Lego city. This will show they are up in the sky but still part of your Lego community. Children love this because it keeps their flying Legos flying. This layout also works well with Lego airplanes.
Invent new combinations of Legos and new Lego structures. There are no rules or limits when it comes to creativity. Tear apart your Lego sets and make new things. If your Lego city needs a specific building, tear something apart and make it.
Don't be too concerned about reality when building your Lego city. It doesn't matter if some of the blocks, characters or vehicles are bigger than others. It doesn't matter if the colors of the blocks don't match. It doesn't matter if Star Wars characters wouldn't hang out with SpongeBob SquarePants. This is all about fun and creativity. Remember, these are toys for the enjoyment of children.