Virtual caches are coordinates for a location, which has some other described object. Validation for finding a virtual cache generally requires one to email the cache hider with information such as a date or a name on a plaque, or to post a picture of oneself at the site with GPS receiver in hand. New virtual caches are no longer allowed by Groundspeak, but they remain supported by other sites. The Groundspeak website no longer lists new caches without a physical container, including virtual and webcam caches; however, older caches of these types have been grandfathered in (except for locationless/reverse, which are completely archived). On August 24, 2017, Groundspeak announced "Virtual Rewards", allowing 4000 new virtual caches to be placed during the following year. Earthcaches are one of the two exceptions to the no-container rule; they are caches in which players must answer geological questions to complete the cache. The other exception is for event caches; for an event to qualify, it must be specifically or mainly for geocachers, and must have a minimum duration dependent upon its category (CITO, regular, Mega, or Giga). Attendees of event caches can log that they 'attended', which will increment their number of found caches. Groundspeak created a waymarking website to handle all other non-physical caches.