This building at the Seaside Park Valmer and aims to determine the mean level of the Mediterranean Sea. This level is used as reference to set the altitude 'zero' of France. Today the building is still maintained by IGN and therefore constitutes the longest extent of the Sea on the Planet!

The measurement sequence was determined that zero altitude was performed for 13 years from 1 January 1884 to 31 December 1896.

The building is now listed historical monuments.