The Mansions in Hydra are three and four-storey imposing and austere buildings, closely related to the glorious history of Hydra. They were built in the late 18th and early 19th century, an era of economic prosperity for the island, thanks to trade and shipping, and bear Genoese architectural elements. The wealthy ship-owners, having traveled a lot, wanted to "introduce" into Hydra features of the European architecture, to join in the lifestyle of western bourgeois society, as the writer George Procopius tells us in his study "The architecture of the mansions of Hydra ".

On the east side of the harbor you can see the Mansion of Lazarus Tsamadou, which today houses the Merchant Marine Academy, which keeps alive the maritime tradition of Hydra.

Over the waterfront dominates the historic Mansion of Lazarus Kountouriotis, which operates today as an annex of the National Historical Museum. Built in shape Π, painted with natural ocher and furnished, it shows us the room where he spent most of his time and other interesting rooms like the shrine next to the entrance and the smoking room.

On the western side of the city you can see the historic Mansion of Frangiskos Voulgaris, one of the great mansions of 1800, which today houses the Villa Hydrea. It has oriental elements such as wooden ceilings of Ottoman Rococo. Also stands out the marble fountain in the ballroom with the loft for musicians and oil paintings of nautical themes. The Mansion frames large wooden windows looking out over the harbor, as well as charming terraces.

On the western side of the city you can see the four-story Mansion of Tompazis, in Italian style, built by Manolis Tompazis and his wife Xanthi Sahini, and already owned from 1936 from the School of Fine Arts and works as annex to it. Today its rooms serve as hostels for budding artists who come to fight with the colors and magic of Hydra. The roofs and the wooden doors inside are new and the living room upstairs is considered the most authentic room. From the ceiling it has been rescued the four corners and the central rosette.

Behind the Mansions of Voulgaris and Tompazi, on the fortification hill among pines and spectacular views, stands the Mansion built by Georgios Kountouriotis, one of the largest owners of Hydra and active politician during the Greek Revolution. Later the Mansion was inherited by his grandson, Paul Kountouriotis, admiral during the Balkan Wars and the first President of the Greek Republic. Each of the windows, if open, "frames" perfectly the landscape, like artwork depicting the sea and the picturesque village. Today it operates as the Museum of modern history of Hydra.

In the same area there are the Mansions of Votsi and Economou, and other old mansions of some historical persons, who lost their fortunes turning their commercial ships into warships for the Revolution, and have identified their name to the independence of Greece. Residents of the island, which until then built their homes with the characteristic whitewashed terraces, quickly copied the four-sided roofs of these Mansions, so the town of Hydra took the familiar image that has got today.

"If you start noticing the details, the Hydra is inexhaustible," says visual artist Dimitris Antonitsis as we enter into one of the old Mansions of Kriezi family, smaller in scale but very special for the respect with which it has been approached by the important American artist Brice Marden (its current owner). All of its rooms have been preserved with almost touching diligence.

Neoclassicism embraces large mansions, such as the Mansion of Georgios Sachini and Eleni Theodoraki, located behind the tavern "Xeri Elia".

West of the city, outside the village also stands the Mansion of Bountouri, featuring a small garden and a private chapel.

In the district "Kala Pigadia" there is the Mansion of Gkorogianni, which there is a characteristic living room of Macedonian type.

In the Kaminia location, it is situated the  Mansion of Theodorakis (brother in Law of Kriezis), which today houses the Nursing Home of Hydra island.