While walking on the promenade, along the Danube River, consider having a look at this vintage steam-powered train engine, dating since the 30s. Such train engines were actively used through the mountain and hilly areas of the country, between 1919 and 1980, for heavy hauling freight and passenger trains. This one, in particular, operated only between 1932 and 1980 and has been brought to Tulcea in 2007.
The train engine is placed next to the Train Station and very close to the oficial bus station, so one can't miss this one while visiting Tulcea.
You are looking for a white plastic container (like a vitamin box) placed somewhere on/inside the old train engine (no magnet needed, it just lays there). Pay close attention to the hints and spoiler image. The cache is meant to be an easy to find. Please leave a note in case that you're in need for more spoilers.
P.S. Take advantage of the fact that coordinates are really precise. Enjoy!