As part of an investigation about the local environment, learn about animals that live underground. Investigate where the rain goes, locating drains in the school grounds. As part of fieldwork investigation of your area, mark on a street plan evidence of drains, telecom boxes, water and gas markers.
Find out about London's hidden rivers by visiting: www.heritagemagazine.co.ukmap800.html Draw these on a plan of contemporary London (PoS 2d, 2e). Learn about topological maps by comparing the London Underground map with places on a "real" map (PoS 2c, 2e). Search the web to find cities that have an underground. Record these on a world map (PoS 1c, 1d, 2e).
Use opal mining in Coober Pedy, Australia, where most people live underground, as an example of primary industry or people's adaptation to the environment: www.walkabout.com.aulocationsSACooberPedy.shtml
Limestone scenery can be a physical geography topic in its own right or it can support a study of tourism. Use some less visited caves as case studies, such as Belize: www.belizex.comcaves.htm