I actually didn't plan on going to Odessa. I love Kiev and spent a week there a few years ago almost feeling like a resident living in an apartment at the golden gate and leaving a coin at Panteleimon every morning on my way out. From Kiev I wanted to take the train to Tiraspol (Transnistria) but it was already sold out. Kind of surprising really but instead I took a flight to Odessa and took the train onward from there after a day looking at the town. It was better than the long train journey.

I believe there are already way too many "historic centers" on the WH list. It's maybe unfair to Odessa because some historic centers around Europe suck and got their status earlier when no comparison studies were requested or made, because Odessa is nice to spend time in and check out the buildings while just having a nice relaxing day to walk around, have some food and drinks, well, the typical "old town" affair I suppose. To quote Wikipedia: "Its historical architecture has a style more Mediterranean than Russian, having been heavily influenced by French and Italian styles. Some buildings are built in a mixture of different styles, including Art Nouveau, Renaissance and Classicist.." It was also mostly spared in WW2 and retains the original buildings. Probably should be a WHS a couple of decades ago.

Don't forget to visit the Pushkin museum.