Talk of architecture in Japan tends to head in one of two directions — the very, very new (as in the mind-bending flagship stores for fashion brands in Ginza), or the very, very old (as in temples dating back centuries). So what, exactly, happened in between?

Well, if you're talking about Tokyo, two catastrophes are what happened: The Great Kanto Earthquake of 1923 and the Allied bombings during World War II. The former wiped the slate clean, if you like, for a rush of inner-city reconstruction mostly in stone and brick, while the latter whittled those projects down — to the strongest and the luckiest.

Open! Architecture, a brand new event set for May 15 to 17, gives the public a rare chance to see inside several of Tokyo's grand old architectural gems, many of them dating from the 1920s and 1930s.

One of the stars on show is the Mitsui Honkan (Mitusi Main Building), which was built in 1929 in Nihonbashi. Presumably still nervous after the 1923 earthquake, the owners, the Mitsui conglomerate, requested their American architects (Trowbridge and Livingston) to make the building capable of withstanding an earthquake 10 times stronger than that on which laws of the day were based. Hence the seven-story building's stocky appearance and its manic application of Corinthian columns.

Other highlights include the Mitsubishi Soko Building (Nihonbashi; built in 1930), St. Luke's International Hospital (Tsukiji; 1932) and the Diet building (Nagata-cho; 1936).

Access to each of the 24 buildings on show requires a reservation in advance and may be possible at special times only during the three days of the event. Details available at open-A.org/

Open! Architecture is a precursor to one of the biggest architecture events in the world — the triennial congress of the International Union of Architects — which will be held in Tokyo in 2011.