The hotel has two types of rooms available - Standard Double Rooms and Standard Single Rooms. The Standard Double Rooms are double occupancy and have a size of 215 sqft. Smoking is not allowed in these rooms, and they have a queen-size bed. The Standard Single Rooms are designed for single occupancy, have a size of 172 sqft, and also do not allow smoking. These rooms have a twin bed.

From the provided data, guests at Pension Unterstein can spend their time at the hotel enjoying skiing and relaxing on the sun deck. These are the featured amenities mentioned in the data.

The hotel is located in a skiing area, which suggests that guests can take advantage of the nearby ski slopes and engage in skiing activities. Skiing is a popular leisure activity, allowing guests to enjoy the winter landscapes and have fun on the slopes.

Additionally, the hotel has a sun deck, providing a place for guests to soak up the sun and enjoy the scenic views. This amenity offers a leisurely option for guests to relax and unwind, whether they choose to sunbathe, read a book, or simply take in the fresh air.

Based on the given information, these are the activities that guests can partake in at Pension Unterstein.