A meridian is the half of an imaginary great circle on the Earth's surface, terminated by the North Pole and the South Pole, connecting points of equal longitude. The meridians divide the Earth as if it were an orange with buds.
A meridian that receives special name is the one of Greenwich, in reference to the city of the same name, in England.
Not so famous as the English brother, but not least important, the 51st meridian West crosses several fjords in Greenland, the Linconl Sea and the Atlantic Ocean.
In Brazil, the 51st meridian West crosses several states: Amapá and Pará - where it cuts the Amazon River and multiples islands -, Mato Grosso, Goiás, Mato Grosso do Sul, Minas Gerais, São Paulo, Paraná, Santa Catarina and Rio Grande do Sul - crossing also the Lagoa dos Patos.
This cache is close to where the Meridian crosses the municipality of Nova Petrópolis to remind us of the importance of these invisible lines in our daily lives, and even more in the scope of Geocaching.
Sources: https://pt.wikipedia.org/wiki/Meridiano_(geografia)
https://pt.wikipedia.org/wiki/Meridiano_51_W