in 5.7, using the standard "elemental" theme you can add a template to your navigation block.
First you add a navigation block to your header.
Then you can edit the design & template of that navigation block
under "options -> custom template", you choose the "Responsive Header Navigation"

I'm sure, more templates and/or navigation blocks will be available in the future.
also look here:
http://www.concrete5.org/documentation/using-concrete5-7/in-page-ed...

in 5.6, there are a number of themes and add-ons that support horizontal navigation.

Does this also work for 5.7.2? I don't see where to pick a custom template.

see the attachment

Thanks for the screenshot Willem. This is what mine looks like (5.7.2), weird isn't it?

In Edit mode:
Click the navigation menu you want to be horizontal.
Click Design and Custom Template.
Click the last icon on the toolbar (wheel/advanced icon)
Change Custom Template
Responsive Header ...

As you can see on the image I have posted, it's not there. :( Are there ready to go templates usually? I'm running a clean install.

Fixed it:
I had to turn on 'advanced permissions'. I fixed it by mistake. Thanks everyone!