PHOTOS: Japan’s ACROS Building is a Mountainous Green-Roofed Pyramid Planted With Trees

Can you imagine stepping out of the subway to go work at a mountainous green pyramid planted with hundreds of trees on every level? Well that's exactly what hundreds of employees experience each morning when they head to work at the ACROS building in Fukuoka, Japan. We've written about <a href=""http://inhabitat.com/acros-a-giant-japanese-pyramid-blanketed-in-green-grass/">ACROS</a> before, but this past week we were finally able to visit this <a href="http://inhabitat.com/acros-a-giant-japanese-pyramid-blanketed-in-green-grass/">massive pyramid blanketed in grass</a> and climb up its zig-zagging stairways ourselves! Click through our slideshow for a personal tour of this fascinating building.

Things have changed since <a href="http://inhabitat.com/acros-a-giant-japanese-pyramid-blanketed-in-green-grass/">we last wrote about ACROS</a>.

When the building, which was designed by <a href="http://www.emilioambaszandassociates.com/portfolio/portfolio.cfm?Pid=7">Emilio Ambasz &amp; Associates</a>, was first built, many of the trees that make up its "step garden" were still saplings.

Now, many of the plants are so tall that they obscure the stair railings, which were clearly visible just a few years ago.

In fact, you have to crane your neck to see over the trees as you ascend the leafy levels, and at times you feel as though you're basically standing in the middle of a miniature forest.

We spotted buzzing<a href="http://inhabitat.com/its-official-cell-phones-are-killing-bees/"> bees</a>, flora of all kinds and crystal clear waterfalls as we walked up ACROS's stepped facade.

When it was first built there were 76 varieties of plants, including 23 different kinds of trees ranging from plum to maple. According to the informational sign (translated by my mom), even more species came to thrive on the <a href="http://inhabitat.com/green-roof/">green roof</a> as they were introduced by visiting birds, and now there are 120 varieties and 50,000 plants.

Underneath its vertical forest, ACROS features nearly one million square feet filled with office space, an exhibition hall, a museum, a theater, conference facilities, a parking lot, and shops.

The glass-clad main atrium lets in tons of natural light.

Visitors who make it to the top of <a href="http://www.acros.or.jp/english/">ACROS</a> will notice that the grey spear that juts out of its facade is actually a stadium-style seating area.

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