Pick a location. (And secure permissions for building on it!)
Gather materials. Find representatives for artifacts and architectural, faunal, and floral remains.
Set the foundations of an ancient city from time period of your choosing. (See the BAS Library for possible site plans.)
Plant fake artifacts and the floral and faunal remains among the architecture.
Get friend with bulldozer to bury everything with dirt.
Repeat Steps 3–5 for each time period you want to explore.
Recruit volunteers and start excavating!