Where I live, it's more or less mountainous (highest mountains about 3000 ft), but with broad valleys with farmland. Valleys vary from about 100 to 800 ASL. So for putt-putt sightseeing, usually around 2000 ASL in the valleys; plenty of emergency landing fields; and in the St. Lawrence Valley, well it's one big emergency field. If I have non-aviator pax, I go up to at least 3000 ASL to get out of the chop. Cross-country, I play it by the winds for best efficiency and speed. Areas with few emergency landing choices, higher.
There is a sightseeing circuit around downtown Montreal. Very popular day and night. They start stacking us in the circuit at 1500 ft ASL (about 1200-1300 AGL), at 500 ft intervals, or even at 200 ft intervals if it is really busy. I entered the circuit with non-pilot passengers once at 2000 ft, at night; ATC offered me 1500 if I wanted to as there was nobody below me. I said "no thanks". The pax could see just fine at 2000 ft and I didn't want to give up 500 ft of decision-making time in the event that the squirrel in the cage got tired. In fact I would have taken higher but there were planes stacked above.
I did have emergency landing sites picked out just in case; a few wide boulevards and expressways, and the docklands. In fact last year a C172 managed to do an emergency landing on a downtown boulevard. Nobody was hurt. Only damage was a dinged wingtip from a street sign. Plane had to be dismantled to get it out.