I got out our blocks, our dinosaur hunter items, some small wooden train set pieces, and later on I got out our old school Fischer Price City (it was mine). My boys had a blast!
It is simple, and yet it engaged my boys for hours. They would walk away and come back for more. Today we moved it from the living room to their bedroom. At 8 am they were playing like mad. It only stopped to take my oldest to school.
Have you made roads with painters tape?