Civil weddings on Hydra Island (also known as political or registry weddings) are conducted by the Deputy Mayor of Hydra. You can use the Municipality (Dimos) meeting room to hold your marriage service or any of the outside areas owned by the Municipality of Hydra FREE of CHARGE. This includes any of the island's beaches, the Periptero (band stand above Spilia) or the open squares around Hydra. (Not the Miaoulis Memorial Terrace.)
Alternatives to public spaces also include: at a restaurant or hotel (inside or in their courtyard), or private house, or private terrace, the roof terrace of the Museum or even on a beach or hillside - so long as you have the agreement of the Registrar to attend you there. Municipality spaces are free of charge. Other places are negotiable on price such as private houses or restaurant's unless you are holding your reception there.
For lots of ideas and insider knowledge about the pro's and con's of various locations, plus full contact details to book your registry wedding AND how to go about getting your paperwork in order, the wording of your ceremony and much more, please see my Online Consultancy Wedding Planner service.