MILLIONS of tourists visit Venice’s beautiful waterways each year.

However, unusually low tides have crippled the gondolas and water taxis, exposing the filth and mud at the bottom of the canals.

This is the second year in a row the phenomenon has occurred, which is shocking considering the maze-like city has been sinking for decades.

Throughout the 20th century, wells were sunk into the Venetian Lagoon to draw water for local industry, causing the city to drop.

The wells were banned in the 1960s, but by then the damage was done.

Venice is frequently plagued by low-level floods, and the ground floors of many old homes have been inundated and rendered uninhabitable.

Studies indicate that the city is sinking at a rate of one to two millimetres a year.

In 2003 an engineering project to prevent flooding was started to raise mobile gates to separate the lagoon from the Adriatic Sea when the water is too high.