Parc de la Ciutadella is a highly rated running spot with a soft surface. It could be suitable in the winter time as it also has has electric lighting.
If you want to do more than just going out for an easy run there are some good options available.
Running in a new city in the winter time can be tricky. Bad weather and darkness make it hard to find good places to run.
Try Montjuïc if there is snow and ice outside. It is usually kept clean.
The line represents the average temperature. The faded area represents the most likely temperature span. The temperature is within this area 80% of the times.
The line represents the average dew point. The faded area represents the most likely dew point span. The dew point is within this area 80% of the times.
The line represents the average wind speed.