Remark: the telescope nearby the cache is not the MERCATOR telescope but the JKT (Jacobus Kapteyn Telescope), the MERCATOR telescope lies a bit below.
This is a traditional cache: a plastic box with a logbook, a ballpoint and a couple of trading items. The cache is located close by a long distance hiking trail, at an altitude of 2360m. You can park your car at the Roque de los Muchachos parking lot on top of the island and follow the trail down from there or you can park at the Mirador de los Andenes parking lot and walk the trail up. The observatory roads are for observatory staff only! The access barrier to the observatory site is closed from 8pm till 7am!
Good hiking boots are a requirement. While people are sunbathing at sealevel, it might be raining or freezing at the Roque de los Muchachos, so dress accordingly! Be extremely careful in winter as snow may cover the cache site. Don't forget to wear plenty of suncream: at this height, the sun can be very dangerous and powerful, even in winter!
From the cache location you have nice views over the telescopes of the Roque de los Muchachos observatory on the one hand and the Caldera de Taburiente on the other hand. If weather permits, one can discover Tenerife in the distance. The cache is named after the famous Flemish cartographer Gerardus Mercator (1512-1594) who studied and taught at the University of Leuven (Belgium). The nearby Mercator telescope is operated by the University of Leuven.
To look for the cache, DON'T go towards the Caldera! The cache is hidden on the other side of the path, AWAY from the Caldera at a safe distance. Don't take any risks and always watch your step instead of blindly following the arrow of your GPS!