Complex sentence: The ship visited numerous ports but one of the most interesting was a visit to the Russian port of Vladivostok, an important Russian naval base and was important for the fact that it was the first visit by a Royal Navy vessel in over 100 years.
Split into simpler sentences: The ship visited numerous ports but one of the most interesting was a visit to the Russian port of Vladivostok, an important Russian naval base. The visit was noteworth due to the fact that it was the first visit by a Royal Navy vessel in over 100 years.