You mentioned you enjoy walking/biking, so this may interest you: Sundays in Bogota host the Ciclovia, where they close major streets for bikes. Locals and families ride bikes, walk, jog, etc. There's stores and stands where you can rent bikes. If your large bags are checked through but you're willing to either wear or pack bike-appropriate gear in your carry-on, you could join the crowds. Not sure if any of the lounges at BOG include showers to clean up afterwards!

Info on tours, rentals, etc. here: http://www.lan.com/onlyinsouthameric...-bikes-bogota/