A Number line you can add to the wall of your classroom.
I have color coordinated the wall to groups of 10. For example, 1-10 is red, 11-20 is orange. This also reflects 100-110 is red, 111-120 is orange.
In the classroom this is displayed at student eye level and we play games such as less than, greater than. Also I use place value for who am I games, such as I have a tens place value of the number 5 and a ones place value of the