Overlooking the harbour just north of the gates of the Dahlak Hotel is the Imperial Palace, the original iteration of which was built by the Turkish Osdemir Pasha in the 16th century. The present building dates from 1872, when it was built for the Swiss adventurer Werner Munzinger. During the federation with Ethiopia, it was used as a winter palace by Emperor Haile Selassie, whose heraldic lions still decorate the gates and by whose name the building is still commonly referred to.
The palace was badly damaged during the Struggle for Independence, and its present state gives a very vivid introduction to how all of Massawa looked shortly after the war and what to expect of much of the Old Town.
It's usually possible to wander around the grounds, as the gates are rarely locked.