Kilkenny Castle is a 12th century castle, remodelled in Victorian times and set in riverside parklands. Once the principal seat of the Butler family, Marquesses and Dukes of Ormonde, this fascinating building is located in the heart of Kilkenny City.

Located on the right bank of the Tiber River, guarding one of Rome's oldest bridges, the Castel Sant'Angelo is an imposing cylindrical building, initially commissioned by Emperor Hadrian as a mausoleum for himself and his family. It was later converted into a fortress, a papal residence, and a prison. Now, it's a museum offering beautiful views of Rome.

Reservations are required for guided tours of the Fred Lawrence Whipple Observatory, but you can stop by the visitors center any day to explore its educational exhibits, including some chronicling research projects conducted at the Arizona observatory. The FLWO is run under the auspices of the Harvard-Smithsonian Center for Astrophysics.

Witnessing the age-old craft of leather treatment at the Bab Debbagh tanneries is a fascinating experience. Situated near a river for water supply, these tanneries have been operating for centuries. The distinctive odour, resulting from ammonia used in the leather-softening process, will let you know you've arrived. Unlike some other Moroccan tanneries, the focus here is on treating leather in its natural state; the dyeing happens elsewhere. Visiting the site can be a bit tricky due to the presence of unofficial 'guides' demanding payment. If you prefer a hassle-free experience, consider hiring a certified guide as part of a medina tour. Otherwise, prepare to navigate past these unofficial attendants by offering a small tip and insisting on entering without their assistance.