Vala came out of Gnome/Gtk app development on Linux IIRC. It takes the GObject object layer from Gtk/Glib and promotes it to a first class part of the language: There’s a fairly direct translation from the various parts of the Vala language to C + GObject / Glib / Gtk+.

I don’t think it’s widely used outside of the Gnome desktop world, but there’s quite a few apps written in it out there.