This was our first attempt at a really large build after we got carried away with our Rokenbok purchases at Christmas. The idea was to build two cities, affectionately named "Blue City" and "Red City", both of which connect to a 3-story bridge in the middle. At the end of the top level of the bridge is a water tower that can be dumped into by an RC loader. This water tower is the centerpiece of a game that the both cities are designed around. Here's how the game works:
Blue City and Red City compete to deposit Roks of their respective colors into the water tower (Blue City collects blue Roks and Red City collects red Roks) -- the team with the most Roks in the tower at the end of an alloted period of time wins (we block the bottom of the tower so it won't dump out except through the push chute on the front).
Red City begins with its Roks mixed with barrels in a big quarry that must be processed through the recycler before sorting. Once Red City has separated the Roks from the barrels, the Roks can be sorted through a double Rok lift, an action factory or a conveyor. Each mechanism of sorting sends the red Roks somewhere where they can be collected and brough to the water tower, but the blue Roks are always dumped into a trap where they are removed from play.
Blue City is similar, except that the Roks start on the third level in the warehouse, and must be carried down to the blue double Rok lift or or processed through the Piston Plant. Again, blue Roks are collected and deposited in the water tower, red Roks are trapped and taken out of play.
We spent close to two months building these cities. My oldest son, Willem (age 6) was the engine behind most of the ideas and provided much of the labor. Our younger kids, Henry and Alyda, have spent hours and hours playing with it, even though Henry isn't even old enough to control the vehicles (he likes to drop the Roks down the chutes).