Stadia and other activity surfaces are provided comprising natural turf. Natural turf units are provided which are transportable between first and second locations, the second location being for the growth and maintenance of the turf unit; the first location being a location for the performance of the desired activity. Means of transporting the units between the first and second locations are also provided. Artificial plant growth media are also provided comprising sand fractions and at least about 30% of shaped pieces of expandable polymer which are substantially inert to plant growth chemistry. In accordance with preferred embodiments, domed stadia are provided with natural turf activity surfaces which are able to withstand intensive wear during multi-season activities.