Destroy a map?

Hi,

How do you properly destroy a map, to free up the memory? I have an app I'm working, and it annoyingly requires me to re-init the map every time (as the div its showing in, is a popup modal that doesn't remain in the DOM). As such, I want to make sure I clean out the map from memory when closing the modal the users use. I can't find anything about destroying it though in the documents?

Thanks

Andy