The Rock of Monaco (French: Rocher de Monaco) is a
141 meter (459 foot) tall monolith on the Mediterranean
coast of the Principality of Monaco

Today, the Rock is in the oldest of Monaco's four quarters, Monaco-Ville,
which is also the location of Old Town, the oldest part of the city.
This is not far from the Prince's Palace, home of the current monarch, Albert II
and the princely family, the Cathedral, the Oceanographic Museum of Monaco.

The Rock of Monaco is a popular tourist attraction to go
see the palace or the changing of the guards

from: Wikipedia