What sort of snake lives in ponds in Romania?

I was recently in Bucharest, the capital of Romania. I decided to take a walk through a park, where I found a dried up pond, I was looking into the dried up pond and saw a small, thin brown snake, roughly around 50 cm long. I could not see any markings on its back, however I was quite a long way away from it so it could have had some type of markings. After around 5 minutes of watching it slithering around the dried-up pond, it went under a set of rocks and I didn't see it again. I just wanted to know what sort of snake this could be, as I am curious to know what it could be