At the southern end of Porto Cristo you will find the Caves of Drach.
The caves may not be the largest on the island but they are certainly the most impressive and the most commercialised. There are only a few guided tours each day so check with the tourist office for times before you set off. The tour will last almost an hour. You descend into the caves by means of steps, following a guide. As you make your way underground you will note that regardless of the outside temperature, in the caves it is constantly 22 degrees. So you will not need a coat. You will however benefit from sensible footwear.

When you reach the bottom of the caves you will sit in a specially constructed auditorium, in front of the Martell Lake. When the lights go out, the lake is illuminated and you are given a short classical concert by a string quartet as they float past you on illuminated boats.

There is a restaurant near the entrance and very clean toilets. There is ample, well organised parking. Either make your own way there or take one of the many coach trips that include the port.

We have visited the caves on several occasions and comment on the following;
Although the visit is very interesting and entertaining, we thought it was a little expensive at 7.5 euros each and we were very disappointed to find that you are not permitted to take photographs (and the guides are very strict on this) - how mean of the local authorities. Needless to say we wouldn't purchase a postcard on principal.