Honestly, my husband and I loved Madre's Restaurant which is J.lo's restaurant. SO romantic! They have a trio there to sing to you while you eat if you like and the setting is so pretty. Food is also good.
Inn of the 7th Ray in Topanga Canyon... they have a website, check it out, but trust me there is nothing more romantic (people have weddings there & i'm sure lots of proposals occur as well)... and ask for the gazebo, they will probably just make a note & not promise it to u but most likely u can get it when u arrive. if u r looking for more trendy, katana is fun but loud. Good luck!
I second Madre's in Pasadena, Inn of the 7th Ray and Geoffrey's for pretty and romantic restaurants. One of my favorite local places is Amici in Brentwood (it's on the corner of San Vicente and 26th). It's not very fancy, but it is very cozy and inviting. I also love the Polo Lounge in the Beverly Hills Hotel - it's not cheap, but I think it's a great place for lunch (and for people watching!). Be sure to ask for a booth.
i agree with mara--i think the little door on third is probably the most romantic of the places mentioned. there's also il cielo in BH, which has the same kind of vibe and pretty good italian food.
i never really thought of the beverly hills hotel as romantic before, but it totally could be! it's open late and there's a piano player singing and an old-school kind of bar vibe to it--you could definitely kind of snuggle in there and have a romantic time. i used to go all the time, but haven't been in about a year or so now.
inn of the seventh ray is also very romantic, just be sure to go when it's nice so you can sit outside. word to the wise on the food, however--it's mostly all vegetarian (or is it all veg?) and the vibe is a little more new-agey than some people care for. there's another one called four oaks, in beverly glen canyon, that is widely thought to be the most romantic restaurant in the city--i have heard it is wonderful (very pricey) but i can't say because i have never been there myself. yamashiro in hollywood is romantic (if overpriced because the food is definitely not great)--they have the best twinkly city-lights view and you can take a little stroll around their gardens after you eat.
ooh! i thought of another one as i am typing this--g. garvin's (also on third). it's really dark and clubby and sexy, and the food is updated comfort food. it's very romantic.
i also have to disagree with the katana idea--it is a really fun place and the food is fantastic, but it is not romantic at all. as crystal said, it is very very loud, and very very scene-y. if you are coming to LA for a vacation, i definitely recommend it for a people-watching, fun experience, but not for romantic-date-night.
the Hotel Bel-Air is absolutely beautiful, elegant and peaceful - you feel like you're this oasis from the moment you turn onto the tree-canopied road that it's on. sorry to sound like I commercial, but I love this place! my husband & I had our wedding there. the restaurant is beautiful, but if the weather is right, you should try the Terrace for brunch or lunch.