Tangentially, that sure is one giant slab of a hotel.

Er, two giant slabs, I guess.

Yeah, for serious. Ick.

I think the ã on the logo is just a design choice.

I don't think Portuguese uses ã at the end of words, but I could be wrong. I've never seen Spanish use ~ other than on an ñ.

The tilde only ever occurs on 'n' (as ñ). Tildes are not used in lieu of accent marks (besides, that wouldn't be something like allographic variation, it would be more like free variation).

I don't know why the page has a tilde over the "a." It is possible that the acute accent would render the letter on which it occurs as shorter (where the a + accent is the same height as the adjacent letters) or that it would make the vowel + accent higher than the adjacent letters. In either case, there may be some aesthetic reason for replacing the acute diacritic with a tilde.

Agreed. The tilde can only occur on top of the 'n'. And you're right that accent marks cannot be replaced by tildes in Spanish.

Now for the answer. Meliã hotels are part of a bigger group called Sol Meliá. Take a look at Sol Meliá's homepage:

http://www.solmelia.com/home.htm?idLang=en

At the bottom of the page you see "Our brands", and Meliã is mentioned second place. So Meliã is not Spanish, it is just a way to get a new brand keeping its name close to the original name: Meliá.

Aha. I got as far as Sol Meliá on Spanish Wikipedia, but I didn't go to the homepage or find the second brand. Thanks for assuaging my curiosity!