Karlín in Prague
Why locals love it
Karlin is thought to be the third up-and-coming place in Prague after Krymska and Letna (it still hasn't happened yet though). It was the first suburb of Prague and has a wide array of more modern styles of architecture. It suffered massive damage during the flood, as it sits quite low, but has mostly been repaired.
Why you should visit it
There's the beautiful church of St. Cyril and Methodius, which serves as an excellent example of Neo-Romanesque architecture. The neighborhood is also flat and good for walking, with several affordable eateries.
Great place to stay - cheap places to eat and well connected to downtown.