I have found two trolley bus systems in Bulgaria, and nearly fell off my bike at the sight as I’m a nut about them. Didn’t get a chance to do any serious watching or riding but they were the cleanest towns too. Bulgaria was a surprise once out of the stalin type towns with half finished overpriced hotels that had `special` prices for tourists. Maybe that is why we were the only ones.
The hill areas towards Greece were spectacularly nice but the hydro works underway may change this. We were invited into a school in this area and caused chaos and had coffee with the teachers. The blow up globe was useful in explaining our trip and where NZ is.