Opinions vary regarding what exactly was placed inside the Ark: Some authorities maintain that the first set of tablets broken by Moses were inside the Ark, along with the second intact set, and the Torah Scroll which Moses wrote. Hence the name "the Ark of the Covenant" or "the Ark of the Testimony." The shape of the two tablets was square, and they were placed on the bottom of the Ark. However, a different opinion states that the broken tablets were kept in a separate Ark, that the Torah Scroll had its own special place on a shelf alongside the Ark. (Source: Baba Batra 14). 
Dimensions
Contents:   Part I,    Part II,    Part III,    Part IV,    Part V,    Part VI,    Part VII