Canon law prescribes that Mass be celebrated in a “sacred place” such as a church or a chapel consecrated by a bishop. That is why, for example, there are strict rules forbidding the celebration of wedding Masses at locations such as a beach or garden patio. 

However, canon law also allows for exceptions, which means Mass can be found in some interesting places. 
As a general rule, the Church wants Mass celebrated in the most reverent environment possible, but it also believes it may be better sometimes to celebrate it in a less-than-ideal place than to not celebrate it at all. 
For example,

Praise the Lord