To find all the Lost Artifacts of Europe in “Indiana Jones and the Great Circle,” follow these detailed steps for each artifact:

### 1. Parade Helmet
**Location:** Tower of Nicholas V
**Steps to Access:**
1. **Main Quest Preparation:** Ensure you have completed the main quest item “Bottle of Wine” from the “The Stolen Cat Mummy” mission.
2. **Navigate to the Tower:** Enter the Tower of Nicholas V.
3. **Find the Spiral Staircase:** Go down the stairs until you reach the spiral staircase leading to the underworld.
4. **Ascend Instead:** Instead of going down, look up and notice the broken sections of stairs. Carefully execute a series of running jumps to ascend to the top of the spiral staircase.
5. **Retrieve the Artifact:** At the top, you will find the Parade Helmet waiting on the steps.

### 2. Bronze Mirror
**Location:** Sewers under the Tower of Nicholas V
**Steps to Access:**
1. **Navigate to the Sewers:** Enter the southeastern area of the map and go down the stairs until you reach the sewer section.
2. **Find the Sledgehammer:** Look for a wooden platform where you’ll find a sledgehammer or a similar two-handed tool. Pick it up.
3. **Break Through the Wall:** Search for a fragile wall located in one corner of the sewer tunnel. Use the sledgehammer to break through the weakened wall, revealing a hidden pathway.
4. **Follow the Pathway:** Follow the newly opened tunnel, crouching to pass through narrow grates. At the very end of the path, you’ll discover the Bronze Mirror tucked away.

### 3. Golden Xiphos
**Location:** Sistine Chapel’s bottom floor
**Steps to Access:**
1. **Navigate to the Sistine Chapel:** Go to the Sistine Chapel.
2. **Access the Bottom Floor:** Use the stairs at the rear of the main chapel or through a small doorway located at the southern point of the map to access the bottom floor.
3. **Find the Hidden Painting:** Carefully explore the corners of the room. In one corner, you’ll notice an upside-down painting on the wall. Interact with this painting and turn it right-side up. As you do so, the painting will slide aside to reveal a hidden compartment where the Golden Xiphos lies.

### 4. Venus Figurine
**Location:** Borgia Tower (via “A Nun in Trouble” side quest)
**Steps to Access:**
1. **Complete the Side Quest:** Progress through the “A Nun in Trouble” side quest until you arrive at the Borgia Tower.
2. **Defeat the Kidnapper:** Defeat the kidnapper to rescue Gina’s contact.
3. **Find the Tool:** Search for a tool like a sledgehammer in the vicinity.
4. **Break the Wall:** Use the tool to smash a cracked section of the wall in the room where you encountered the kidnapper. Breaking the wall reveals a hidden area filled with bones. Among them, you will find the Venus Figurine.

### 5. Drinking Horn
**Location:** Museum Wing (via “A Nun in Trouble” side quest)
**Steps to Access:**
1. **Complete the Side Quest:** Follow the “A Nun in Trouble” side quest until you reach the Museum Wing, which connects to the Apostolic Library.
2. **Find the Safe:** Inside, search for a storage area containing a safe. Near this safe, you will see a lamp sitting on a crate.
3. **Reveal the Code:** Turn off the lamp to reveal a code, 7171, that appears faintly on the surface of the crate.
4. **Unlock the Safe:** Input this code into the safe’s lock mechanism to open it. Once unlocked, the Drinking Horn will be yours to claim.

By following these steps, you will be able to collect all five Lost Artifacts of Europe in “Indiana Jones and the Great Circle.”