<!-- Portfolio item --> Wrong :D
<article class="portfolio isotope-item buildings design col-6">
    <div class="image" style="background-image: url(img/portfolio-images/1.jpg)">
    <div class="inner">
        <header>
            <h3>Buildings of Tomorrow</h3>
        </header>
    </div>
</article></div>


<!-- Portfolio item --> Right :D
<article class="portfolio isotope-item buildings design col-6">
    <div class="image" style="background-image: url(img/portfolio-images/1.jpg)"></div>
    <div class="inner">
        <header>
            <h3>Buildings of Tomorrow</h3>
        </header>
    </div>
</article>