Simple structure, no roof and yet it's among the most expensive stadiums ever to be built. How so? Starting today we're going to show you future NFL addition, Santa Clara Stadium.

Courtesy of San Francisco 49ers we can present construction photos of Santa Clara Stadium, a venue that will hold 68,500 people (expandable to 75,000) from August 2014 onwards.

It's hardly beautiful after seeing the likes of Cowboys Stadium or Lucas Oil Dome join the NFL, but this work of HNTB architects is to be a true football stadium (American football, that is) like they used to build it. No roof over stands (seen by many as typically European commodity), no unnecessary cladding on the outside, but a massive cauldron inside with first tier of stands holding 45,000 people just around the pitch. Then a cascade of other tiers upwards and most importantly (or most expensively!) 8-floor building behind main stand with facilities for corporate clients.

This is what inflated the budget of this $1.2 billion stadium: 166 skyboxes, restaurants, party decks, giant videoscreens and innovative solutions – things that may be/seem luxury and aren't all too visible from the start. Thus the rough form that has quite a lot going on inside.

Technically the venue is to be as green as possible and quite literally so – roof is to be covered partially by plants that will help insulate the inside. Rainwater collecting, solar panels – these may be expensive at the beginning, but will start paying off once the stadium is put into operation.

When will that be? According to the schedule in August 2014 and despite construction works having started just in April this year, last Friday workers reached the highest point, making the future venue recognizable already.