Budapest is grand, frequently beautiful and fortunately a bit dingy in the best of ways. You are renting a flat on Csengery utca in a happening, somewhat scruffy area of the city known as Erzsebetevaros. Yes, it's a rather hip part of town these days. Yet your courtyard building gives away no secrets behind its stern and weathered edifice across the street from a vacant lot. The Airbnb flat within is outfitted with all the mod cons, yet the inner courtyard and stairwell could prove a credible location for a film decades if not a century past (replete with a stairwell and corridor to the street so dark of an evening they seem the perfect location for foul play). A great city can paralyze with its choices. So first, decide on a great building and go there. The building in this case, the Geological Institute, designed by the great Odon Lechner, frequently called, if a bit reductively, "the Hungarian Gaudi." Lechner a bright lig...