Corporate office buildings used to offer architects the chance to tap into fat construction budgets and make serious design statements.

In the late 1950s, when Teddy Kollek, the future mayor of Jerusalem, first suggested founding a national encyclopedic museum little more than a decade after Israel won its independence, many thought the idea pure folly.

Sometimes, form follows fortuity. In the 1990s, Rem Koolhaas developed an idea for a private house near Rotterdam; when that project was shelved, he adapted the concept to a much larger building — a concert hall in Porto, Portugal.

Anyone who doubts the relevance of libraries in the age of e-readers, amazon.com, and the iPad should visit the new central branch of the Cambridge Public Library (CPL), in Cambridge, Massachusetts.

Turn the clock back to 1999 and you find Zaha Hadid and her partner Patrik Schumacher working on a critical set of projects, four of which (including MAXXI) eventually got built and two that never moved off the page or computer screen.

In Rome, history flows through every urban artery, providing a strong pulse to obscure outposts and tourist destinations alike.