In university, one year, our building started smelling like there had been a sewage overflow. Pretty soon, everything around started smelling like this - the stores, restaurants, cinema, etc. in central campus was stinking. It was soon found out that the decorative Ginko trees planted in the central part of campus were fruiting (probably for the first time since planting) and the fruit was getting crushed underfoot and carried everywhere. The smell took a few weeks to go away.