Things to do with toddler on rainy day!?

My sitter is taking a once a year and much needed vacation. So I also took a week off of work and me and my son have the entire week together! I had planned lots of pool and outside time and park trips but unfortunately it’s going to rain all week! What are some things to keep him entertained? I plan on going to an indoor playground but it’s 30 mins away and we can’t go every day.