Alpintouren is an outdoor sports website with a database of over 8000 GPS tours for hikers, climbers, mountain-bikers and skiers. The site has long featured Google Maps on each dedicated tour webpage. Now it also has an overall Google Map displaying the over 8000 tours on the site.
In order to display such a large number of markers on one map Alpintouren have devised their own clustering solution. The site have also designed their own custom markers so that users can differentiate between the various type of tracks available.
via-ferrata.de - Google Map mashup of climbs in the Alps