Seen from above, Sofia, Bulgaria, looks less like a city and more like a forest. Large "interblock park" green spaces between big apartment structures are a defining characteristic of the city. They're not so much "parks" in the formal sense, with fences and gates, just open green areas growing up in interstitial spaces left behind.But as green as it still looks today, Sofia used to be even greener.  Since the fall of Bulgarian communism in the late 1980s, Sofia has lost more than half of its green space. To understand why, one has to look back to the founding of the city in the Soviet era.Between the Blocks